Loss Of Dsl Connection

I don't know what is causing my problem but it began several months ago after installing microsoft's SP2. My internet connection is through DSL, I am able to stay connected if I am actively using the internet but if I leave my computer unattended for about 20 minutes I lose the connection and need to reboot the computer to gain the connection again. My DSL provider, SBC has checked the line and state my problem most likely is due to corrupt files possibly something called a pcpip, which means nothing to me any ideas and how to begin troubleshooting this issue?

I would run winsockfix for SP2. Also make sure you first run spybot S&D and maybe HijackThis as well and post