vpn disconnecting w/any TCP/IP activity

We have Windows 98 Workstations calilng from home to an Instagate VPN/Firewall. 99% of the Windows 98 PC’s are connecting fine, but this is what happens with one. They use AOL for dial up to the internet (so does other users with no problems (version 7.0)) then the call into the VPN thru MS VPN created thru dial up. They connect to the VPN just fine but then when they try to do something related like browse “network neiborhood” or access resourse they get disconnected from the VPN (note the dial up internet source). I’ve followed MS’s instructions on compleatly uninstalling dial up/VPN/TCP and did this but still have the same problems. Any clues?