Solved Cannot remote control terminal session in Windows Terminal Server 2008
An administrator user tries to remote control a user session from Terminal Server Management Console and gets error 'Access is Denied'. The user gets disconnected from the user terminal session with the message 'Your Remote Desktop Session has ended. Your network administrator might have ended your connection. Try connecting again or contact technical support for assistance'
Download and install the Hotfix from Microsoft. Here is the URL:
http://support.microsoft.com/kb/2523307
OR