New VPN connection problems

This is a new VPN, and I am having a problem with staying connected. The server is running Windows 2003, and I am connecting with an XP client. Everything goes smoothly, when I click connect (my client connects and authenticates) Once connected I am able to ping the server as well as other PC’s on the remote network from my client….but only for about 20 seconds. Between 15-30 seconds after I connect, the client stops receiving data. The VPN appears to still be connected, but nothing is getting through to the client.

Any advice will be appreciated.

Thanks
chris