Internet Access Problems

This is my first post, and I hope I'm posting in the correct forum (I think I am).

I'm pretty adept with computers, but this is a new one to me, and I can't figure it out for the life of me. Did a search and couldn't find any threads on this.

A friend of mine is using XP SP1 with IE6, Norton Antivirus & Internet Security 2004. When accessing a particular site (not important - it's a reputable site, no malformed code, works for me in every browser I tried), the page will fail to load, and then his entire Internet connection will seem to fail. Internet Explorer displays a Cannot Find Server error on any site he tries to access (that work fine before he visits this particular site). All other programs on his computer (such as AIM) that rely on Internet access will report being unable to connect. However, he still has a valid DHCP lease from his router (and renewing it does not fix the problem), and he can ping sites (and resolve their domain names) through the command prompt. This situation remains until he reboots.

Two other computers connected to his router don't have a problem accessing this site, and there are no settings on the router blocking access to this site.

Any ideas? I'm at a complete loss here - never seen anything like this. TIA for any light you can shed on this.

Could be as simple as spyware, I just had a bad case that would keep closing my IE windows on a constant basis. If it is the same thing I had, use ad-aware to scan the registry as well as the rest of the HD just to make sure there isn't any spyware. Then, manually go through the registry to see if he has any entries that don't belong.

I hope this helps, gl with the fix.