Hi Bernoldi,
You should not rely on the interface seen in GateKeeper; you need to use basic proven networking methods to troubleshoot. I find your description a bit challenging to interpret, you should really use the facts you have gathered instead of an idle description.
1. Can you ping with NetBIOS names? If not can you ping with IP Addresses?
2. Can you access shares via UNC Paths and NetBIOS names? If not can you access shares with UNC Paths and IP Addresses \\192.168.0.1
3. If there is a firewall installed on that computer, but it is disabled, it can still firewall that computer; you usually need to stop it from Starting up with the computer; a classic case is ZoneAlarm.
VPN is working between servers and clients locate at the Host side.
4. There is no VPN when you are within the same LAN; so you are saying on that LAN you can access the shares of the Windows 98 computer from the computer that also has the role of the VPN Gateway; correct?
5. Is the server on the Win98 machine end set to maintain a browser list? (i.e. act as a potential/backup master browser, and is accessible to the other end of the VPN) (Sounds as though the other end is not getting the correct browser list netbios info).