To allow multiple RDP connections to a Windows Server 2008 Server R2
server from the same or different users navigate to the following Group
Policy node:
Computer Configuration\Administrative Templates\Windows
Components\Remote Desktop Services\Remote Desktop Session
Host\Connections\
Now, edit the policy name: “Restrict Remote Desktop Services users to a
single Remote Desktop Services session” and select “Disable”.
In some cases, you may want to prevent an Administrator logging in
remotely from inadvertently logging off a locally logged on
Administrator.
To do this, edit the policy named: “Deny logoff of an administrator logged in to the console session” and select “Enable”.