VPN drops connection to LAN

I have a Sysmaster VPN used to connect to a new installation of Windows 2000 Server on a 30 node LAN. I can login one user and map to a share on the server and am able to ping all LAN nodes. However when I attempt to login a second user the VPN willallow the login but then will drop the connection after about 5 seconds.

I can ping successfully all nodes within the LAN until the 5 seconds are up. My virtual connection still shows active on the remote client but no mapping is possible after the connection is lost.

The VPN is using PPTP and NAT. Is my problem the NAT, PPTP, a missing configuration on the Sysmaster?