why did my device sop working ?

my garmin did the same - died on updating. I tapped the problem into google and up came a long blog from others with the same problem. Garmin replaced it without question.
Apparently if you unplug tomtsom too soon after updating, they die.

sue corbin
January 2009

It could be that you have accidentally muted it, try going into the setup and unmuting, or you have turned volume down so low that it cannot be heard, if it is a touch sensitive screen, touch at bottom of screen and the volume control will appear, (well it does on the Tom Tom one series that I have used) then slide the volume higher by moving it to the right. Hope that helps.

Bigboab
January 2009