You may have to reset the unit - Power off Garmin unit. Press on continuously the upper top left corner of screen and then power on the unit by pressing once on the Power button. You should be prompted to clear all user data, or asked if do you really want to start up in maintenance mode. Press "Yes" to reset (warning: all data will be erased and lost, so backup before proceeding) or enter maintenance mode.
Then, you may have to download the Garmin updater and get any software updates. This should fix it.
Try this before send out to Garmin and if your unit not under warranty
1. open the unit (two screws at the bottom)
2. unplug the battery cable... then wait for 1 min.
3. plug back the cable... don't turn on.
4. hook up the usb cable then upgrade firmware.
5. hard reset the unit.
if still having problem then send them to Garmin for repair
My nuvi 205 died after extended use without a charge. I tried charging it with the car charger but it would't take either. when I got home I was about to throw the unit away, but decided to plug it into the computer with usb port and it started working again. It now takes charges and works well.
I plugged my unit into the usb port on my computer and let it power itself on and that solved the issue.