Test Execution will only work on a remote machine if the RDC window is maximized. Once you minimize the window, execution fails. There are still no reliable workarounds that we are aware of. The following solution has been tried, but is not 100% reliable. 

Click the Windows Start button.
Type regedit in the Run box and press Enter.
Find the registry key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Terminal Server Client
Create a DWORD value with the name RemoteDesktop_SuppressWhenMinimized and set its value to 2.
Find the registry key:
HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Terminal Server Client
Create a DWORD value with the name RemoteDesktop_SuppressWhenMinimized and set its value to 2.

This workaround can be found here: 

http://www.telerik.com/automated-testing-tools/support/documentation/user-guide/knowledge-base/test-execution/no-tests-execute-on-locked-machine.aspx