Magellan Roadmate 6000T problem....

Had a problem with mine last week. Driving to las Vegas from Southern Calif.
I "Muted" the audio with the "Mute" key. After a few "pings" at each turn
the damn thing locks up!
I hit the reset button, it rebooted and i didnt mute it. Worked fine for a
hour. Muted it again...same thing happened. Locked up again.
For some odd reason muting the audio causes lockups. From now on i will
simply turn the audio all the way down instead.