Same problem here, constant reboot:
power on -> garmin screen (splash logo)-> power off ... and so on non stop. tried soft reset( holding power button for 20 sec) does not work, hard reset does not work also, putting finger in lower right corner of touch screen does not do anything. It started doing it after i have started the car, garmin started to initialise itself and then i had to shut car off, after that this problem appeared. So my guess it was not completely initialised and therefore firmware(sys files) got corrupted.
the megaupload link does not work no more...FBI shut it down.
what can be done to revive my unit?
thanks.