Where do the GateWays of the client machines behind the VPN server point to? The router or the WinGateVPN server?. If they point directly to the router or another location that is not the VPN server, you will need to install the RIP 2 client on each client that will participate behind the VPN Server, which is avaialble from here:
http://www334.pair.com/qbiknz/downloads/ripv2client.zip
With regards to the server not being able to open/explore.
1. In the VPN Host properties, what is the "Local Participation" set too?
2. What operating system is running on the server? Small business server?