|nslookup web address.|
Use ip if returned in address line.
Since you say other tcp/ip is working then I assume either dns or port 80 issue.
Guess it could be other if you use proxy.pac file or other odd setup. Most browsers don't fail like that.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10