Simple steps to enable
Multiple Remote Desktop Sessions on Windows Server 2008, try (not in customers server..
)
1. Login to windows server as the desired user, Click on
Start >
Administrative Tools >
Terminal Services >
Terminal Services Configuration2. Right Click on “
Restrict each user to a single session” in the “
Edit settings” section and choose “
Properties“.
3. Uncheck the “
Restrict each user to a single session” checkbox and Click
OK.
4. Click
OK for the window that opens telling "
configuration changes have been made to the system registry...........RDP-Tcp connection will not be changed".
5. You will need to
log off and log back on for the changes to take effect.
NOTE::You need to log off after each session of the remote connection, otherwise it may cause session login issue. 
