Network path not found.

My corporate network is running on an NT 4.0 server. My remote client is Windows XP Pro. With the remote client I can VPN into the network and validate with no problem. I can ping PCs on the corporate LAN so I know I’m connected. But I cannot mapa drive to a shared resource on the server. I get the error message “The network path was not found”. This works fine with a Windows 2000 client but not with XP Pro. I’ve tried the “net use” command from a DOS screen and get the same message. I’ve entered \\servername in Start/Run and get the same message.