Recently I needed to perform a hardware reset on a Magellan RoadMate GPS. Magellan calls this procedure a "reset for first use". If your unit is locked up, or so doing something strange that only a total reset will cure, then this is for you. Note that this will erase everything saved on the unit, and Magellan says you should call their support instead.
Step 1: On the RoadMate, press ++--+-
this will bring up the "hidden menu". From there, you can access the shell, perform a hard reset, and additional tasks on some units.
There - now you know how to access the "hidden menu" on a Magellan RoadMate. Use it at your own peril. Cheers!