check your hosts file. im not sure what it is on windows xp, but on windows 2000 its c:\winnt\system32\drivers\etc\hosts


most spyware/viruses modify the hosts file to prevent you to use windows update, virus updates, etc. this would be a place to look.


also, run a scan on http://housecall.trendmicro.com and maybe that'll catch the virus because many viruses are becoming smarter. they disable firewalls and anti-virus scanners.