vpn – ping and validation problems

Have set up several succesful VPN connetions for clients but this one has me stumped. NT 4 RAS server is also PDC and WINs server. It authenticates both win98 and 2000-wks dun user name and password and allows a vpn connection, however the second domain logon screen fails with “no domain server was available to validate your password…etc.” The vpn remains connected but I cannot ping the ras server or the wins server nor can I map a drive using ip address nor netbios name. Thought it mightbe a gateway problem. Have tried adding various routes and gateway changes but no luck. Anyone seen this before? Would appreciate any suggestions
Tim Barnum MCSE