VPN woes

I setup a VPN at an office and I can connect to it, but I cannot see any shared drives nor computers. Before, I was having trouble with the router before and wasn't able to make a VPN connection to the server from outside the network. If I make a VPN connection to the server from inside the network, everything is fine. Any ideas what could be wrong?

The server is running XP Pro with SP2. The server is connected to an 8 port Linksys switch and that is connected to a Netopia DSL router. The Windows firewall is set to allow VPN traffic through as is the firewall on the router. I've tried the VPN connection from several computers running different OSes, so its not a problem with the client. Any ideas?