When connecting using the VPN on Windows 7, Windows will try to authenticate with the VPN credentials instead of the Domain credentials.
This will give you an error “The specified account does not exist” when trying to access domain resources like file shares.

To solve this problem you should disable using RAS credentials on the VPN connections.

On Windows 7 Execute the following steps to solve this problem:
1. Edit the following file with Notepad.
     C:\Users\UserName\AppData\Roaming\Microsoft\Network\Connections\Pbk\rasphone.pbk
if the file location above is empty you might find the path in the following location
     C:\ProgramData\Microsoft\Network\Connections\Pbk\rasphone.pbk
2. Locate the following entry: UseRasCredentials=1
3. Modify the entry to the following: UseRasCredentials=0
4. Save the file and reboot the machine.