Modular Control System (Navigator) showing 'WAIT'. So can not operate radio/CD. on 2002 Mercedes-Benz ML500

Somehow a message 'WAIT' just came up. I followed the instruction on the manual to rectify it but was not successful. Cut off power by removing Battery terminal and replacing it but still showing WAIT. I got the security code but can not insert it as I cannot get the appropriate message. Thanks.

Asked by for the 2002 Mercedes-Benz ML500