OK, I give. I run into this situation now and again and it's got to be due to a hole in my knowledge of Windows Server OS.
I configure a client on a Windows domain (right now the issue is on a W2K3 server but I have run into the issue on a W2K server as well) and map a drive to say N: \\server01\data
Now I need to allow them access remotely to the drive over a PPTP VPN and don't want to mess about with NETBIOS so I just map another drive letter to the same space via the IP address. For example, I: \\192.168.0.10\data where the IP address is the address of the server.
The user has no problems when they are using the netbios drive letter on the network but when they attempt to use the ip addressed drive letter over the PPTP VPN they recieve a message that says the resource is already in use and they cannot login to the same resource more than once.
OK, so I just map the IP address and let them use I: (ip addressed drive letter) when they are locally logged in. This works fine most of the time but the connection (we are still talking about locally logged in clients) to the drive tends to "drop" and the user gets a message indicating that they do not have rights to the drive.
My objective is to get the PPTP VPN to work (without breaking the local login) but the issue seems to involve my ignorance of NETBIOS.
But to second guess your questions, the VPN server is a Netopia R910 and works great for everything else I do with it. From a remote location, the user logs into their notebook using their username, password, and domain of the server01. Once on their notebook, they start the PPTP VPN to the Netopia. Once there, they should be able to access all the drives etc as the Windows Client should hand the user's credetials over to the server as resouces are requested (right?).
So what am I missing about the difference between mapping a drive letter with a netbios name vs mapping a drive letter with an IP address?