Problem (still) accessing internet across network

Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.

this may help. quoted form http://www.ChicagoTech.net
Can't access some web sitesSymptoms: 1) If you're using MS ICS or Windows
server as router to access the Internet, your clients may not be able to
access certain web sites. However, the ICS host or the server doesn't have
this problem.
2) After installed a new router or cable modem replacing dial-up to access
the Internet, you can't access some web sites.
3) You also find that most web sites you can't access are block to ping or
they are security sites using HTTPS.

Causes: 1) The problem occurs because many web servers block ICMP messages
and the packets are dropped. As a result, the requested web site doesn't
load.
2) This problem is caused also by an incompatible MTU networking setting.
You may try to install the latest SP. If you use MS ICS, you may want to
configure all your Client computers to use the new, lower MTU as the default
for all Internet communication. To modify the MTU size, locate the following
registry key: HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\
Tcpip\ Parameters\ Interfaces. If you use a router like Cisco DSL Router,
you may want to adjusting the PPPoE MTU Size. For example, to adjusting the
PPPoE MTU Size on the Cisco DSL Router, do

interface ethernet0
no shut
ip address ip address subnet mask
ip adjust-mss 1452


--
For more and other information, go to http://www.ChicagoTech.net

Don't send e-mail or reply to me except you need consulting services.
Posting on MS newsgroup will benefit all readers and you may get more help.

Robert Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN, Anti-Virus, Tips & Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.

"BrianW" wrote in message
...
Thanks for the suggestion of specifying the IP address of
the ISP DNS servers, but it didn't solve the problem - I
wonder if I did the right thing. I set the DNS IP
addresses in the TCP/IP properties of the internet
connection on the desktop and of the network connections
on the two PCs. Was this correct?

Thanks for any further help.

Original problem:

I have a peer to peer wireless network between a laptop
and a desktop, both running XP. File and printer sharing
work (thanks to getting tips from this newsgroup!).

The desktop has an ISDN connection and works fine for
internet access. I want to use this connection on the
laptop across the network.

For some websites it works correctly from the laptop, but
for others the progress bar creeps up to 5 marks and then
hangs indefinitely, with the message 'opening' and the
url. Examples are news.bbc.co.uk which works, and
www.amazon.co.uk, antwrp.gsfc.nasa.gov/apod/astropix.html
and support.microsoft.com which don't.

Everything works OK if I connect the laptop directly to
the ISDN line. (I then have to delete the connection I
defined to make it use the network again).

I'm running Norton Internet Security, but I get the same
problem if I turn it off.