I have the same problem described by Sean here:
"I have an SBS server 2003 SP1.
no probs until Friday last week. Open up browser on the server itself and i get cannot display page - dns error. Can access internet etc etc from pcs on network no problem. Antivirus cant update on server as it cant locate update server. I can ping www.google.co.za
etc - just not browse?
Ran ICW - dont see any new errors - anything else i should be looking at?"
In my case,
The SBS server is acting as DNS server for the network and uses itself for DNS. I can ping, my FTP server is working, etc... but I cannot browse. I followed the instructions described in the solution for sean, but no change on mine. Any help much appreciated.