Reset your Nokia:

Switch off the Mediamaster 9800 S.Using the remote control,
The time is shown on the display.
Now press and hold the Program+ button on the Mediamaster 9800 S.
Keep holding the Program+ button and press the Program- button as well.
Keep both pressed until "CUSt" appears on the display.
When you release the two buttons, a message (Pull The Cord) appears on the display.
Remove the power cord from the socket, wait five seconds and then plug it in again.