Cannot send data on Internet after a certain amount of time

I have the most unusual problem and I've been pulling my hair out trying to
get it solved.

I recently got a DSL connection (SBC Yahoo!) after being on dialup, and now
for some reason, after I've been online for a certain amount of time (as few
as 10 minutes or as long as an hour), I am unable to do things like send
email, upload files via the web (i.e. online photo album) or post in certain
web-based forums.

I *AM* however, able to browse the web, upload files via FTP, download
anything, chat, or receive email with no problems at all.

This is extremely discouraging especially when I have to send an email reply
ASAP; I use Eudora 7.0 as an email client, and when I send mail, the
progress bar moves to a certain point, then just stops there.

The ONLY short-term solution is to reboot the computer. After which,
everything works fine...until 10-60 minutes elapses and I have the problem
all over again.

WHAT IS GOING ON??!?!

Here's relevant info as to what I have:
2Wire 1710HG DSL modem (with hardware firewall)
NVidia NForce Networking controller
Windows XP Pro SP2
Norton AV with Internet Worm Protection (outgoing email scanning disabled)
Windows Firewall is currently disabled

I've even disabled power management on the network adaptor driver - problem
still persists.
I've even looked at stopped processes and restarted them - problem still
persists.

I'm normally good at solving my own computer problems, but this has me (and
every expert I've talked to) stumped.
PLEASE HELP!!!!

 

Try using the SBC Self Support Tool. It can usualy cure issues you
may have.