Network Access is limited to administrators

I have a Windows XP machine on a local lan connected with a Hub to a Windows
2003 server running Routing and Remote Access. The Basic Firewall on the
public connection of the Windows 2003 server is enabled. The configuration
has been working for many months now.

A few days or a week ago, it was found that users who previously could
connect to the Internet could no longer connect. However, if the user is in
the local Administrators group they can connect to the internet. This goes
beyond the application layer and Internet Explorer. If you try to PING the
default gateway by IP address, it works - but it cannot translate the IP to
a DNS name.

I created another user, a local administrator only, and the user was able to
do PING, Browse Web, and use NSLOOKUP effectively. What this says is that
the permissions on the Domain are NOT the issue. If they were the local
user, no mater what priveledge on the workstation, would not have permission
on the domain.

Thus, we have a local issue with using services like the DNS Client. I have
disabled IPSEC, even though I do not have any policies enabled. I have
uninstalled the IPv6 which is automatically installed with a service
pack/hot hotfix, and disabled the Internet Gateway Discovery Service.
Nothing seems to help.

I used regmon.exe to check on access to critical sections of the registry
having to do with Networking and TCP/IP, but no access denied messages show
up. I checked permissions on the %SystemRoot%, but they are okay with USERS
given READ/EXECUTE.

I have done some extensive searching on this issue on Microsoft's site and
the web to no avail.

Anyone got any ideas?

Paul