Source URL: http://support.microsoft.com/kb/323597
If we have a broken Terminal Server that cannot issue client licenses - causing RDP connection errors for new client PCs.
Export the "HKEY_LOCAL_MACHINE\Software\Microsoft\MSLicensing" key from a working machine on the network and import it onto the new client PC. This should resolve the RDP certificate issue and allow the client to connect.
NOTE: The real solution would be to resolve the TS Licensing issue - Restore the TS Licensing or re-activate the server using the TS CALs, etc.