This seems to be almost the exact same problem as Slowdler. No resolution seems to be available.
Here is my scenario. I have a DSL modem connected to a WRT54GS router. Computer A had XP all along. Computer B had 2000 but was upgraded to XP. Prior to the upgrade on computer B, computer A had no problem connecting to B to transfer files back and forth and also use the printer connected to B. Ever since the upgrade, A can no longer connect to B.
Whenever an attempt is made the following error msg is displayed: computer A is no accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. The network path was not found.
Both computers are set up with Admin profiles only, thus anyone who logs on has full access to everything. When a ping attempt is made from A to B and viss versa, the request always times out, even though they are connected to the same router and EVEN THOUGH IT WORKED BEFORE!!! NOTHING HAS CHANGED!!!
I logged into the router to see if possibly the router was blocking traffic somehow. Couldn't find anything. I upgraded the firmware thinking this might fix it - nope. Rebooted the router hoping to reset any bogus setting - no luck.