Remote Desktop Disconnected on Windows Server 2003

Hi friends,
We have Windows Server 2003 with SP2 installed in our office.
Our clients remotely log in to the server and then use TS for some applications.
This setup was working correctly for last three months.
Since yesterday evening, one client used by our production supervisor started getting error using remote connectivity. When he tried to remotely connect to the server he got the error…
Remote Desktop Disconnected
The remote session was disconnected because the local computer’s client access license could not be upgraded or renewed.
Please contact the administrator.
Other clients are just working fine without this or any other error. I tried restarting the server as well as the client but the problem persists.
I can try to connect using other user account from the same client machine but again the same error appears.
Any idea about how to restore connectivity as this client is used for production scheduling which is a vital step for our company business.
