interesting network connectivity problem

A Windows 95 client able to connect to shares in its own subnet with no problem. When it tries to connect to the WAN, the other clients are visible (sometimes) but no shares can be opened. All TCP/IP configs are fine and consistent with the others in that subnet (who are not experiencing these problems). Tried reinstalling the drivers of the NIC – no luck. Tried removing and replacing NIC and reconfigure all TCP/IP properties again…. still no luck. Any suggestions would be appreciated. TYIA.