Make sure your DNS server is setup to obtain auto.
Just follow instructoins for the DNS part.
Then i’d check your hosts file, make sure nothing generic is in there blocking all traffic.
http://www.mvps.org/winhelp2002/hosts.htm
If those fail, i’d install adaware or spybot and run a full scan.
If your not familiar with hosts file, then just try the adaware first maybe.