Password problems using VPN

Here is the situation…

Windows 2000 server, service pack 1 installed. Enabled Remote access on server, made a user able to dial in. Static IP address on server, accessed through ISDN router.

From another office, I can connect and login to the server while using a cable modem, Win98se or win2k client.

Win98se clients that use a dial up ISP connection, can attach to the server, but not access any shared directories. trying to click on server asks for a password to $ipc or the shared named. Any valid password returns incorrect.

I have verified this on two dial-up computers. Here is one rub. Both computers had VPN adapters removed. Had to reinstall windows vpn communication, through add/remove programs.

Any suggestions?

TIA