No video or talk

I just not going to give up, maybe someone can make some good
recommendations here. I originally was able to have both video and talk with
this computer but now I can do either. My XP system will not allow
conversation at all. I run the tuning wizard and everything works fine in
WMessenger 4.7 but as soon as I try to have a conversation only with my
brother it simple stops working and my brothers computer says the connection
was disconnected just as soon as he excepts my request. If he sends me a
request as soon as I accept his request the connection is broken. I have
McAfee firewall, a cable router, as well as another wireless W98 computer
using this computer to connect to the broadband cable modem connected to the
XP machine in my house. I can't figure out why the set-up wizard on this
machine using 4.7 works perfectly but when I try to connect to anyother
machine on the internet the request for a talking connect is disconnected. I
can write a message back and forth but can't use anyother feature except for
send an instant message. Both video and audio connections are disconnect as
soon as they are excepted by the other party. I see Mr Kay giving out a
bunch of help maybe you can offer your best guess here it baffling? My sound
card is Santa Cruz (Turtle Beach) who is of no assistance but works well,
the video cam is Intel cheapy but work just fine but ultimetely no help what
so ever, and McAfee firewall and virus scanner, with brain dead help on
line. Thanks to anyone with any suggestions.