This problem has been getting progressively worse since I got my new system. Meaning, at first it would time out or stop responding only intermittently. Now it is ever single time I log on and now I can work for about 90 seconds. I can be on a page or downloading a file (like a critical update) and it will stop responding. It just freezes up. When I try to access any other page I get the "Page not found" error page. Then its toast. I have to completely reboot the system to access any pages - which at this point is worthless. I can't even check my email or pay my bills (so obviously, I am posting this from my work computer and not the one in question).

Other info:

All other system functions operate just fine.
I can log on the internet with no problems at all.
My ISP reports no problems and we have gone through all the XP settings.
I ping them and all the packages are fine.
I have this problem with both the Intel modem that came with the system and with my USR modem.
The browser doesn't matter; I have the problem with both IE and FF.
I was on the phone for 40 minutes with tech support last night who feel this is definitely software, not a hardware problem (I could not get through to software support).
I have scanned for but have not found any viruses, trojans, or malware of any sort (used AVG, Ad Aware and Spybot).
I checked my installed programs and found nothing extra or suspicious.
I have no other firewalls, virus scans or the like running that may be causing a conflict.
I am at my wits end.

Thanks in advance for any help you can offer.