Your GPS is a WIPNav+ or RT6, you have lastest firmware 2.86b.
You have maybe a big problem, I hope the RT6 is not in serious default ?
Did you try to press "eject button" for a few seconds, the RT6 restarts (Hard Reset) ?
You have another reset (Factory Reset), but you need the firmware CD and current maps.
You can also disconnect the battery of the vehicle for 15 minutes.
Be sure to remove the USB drive or CD from RT6 before restart it if necessary.
After that, you can go to see your dealer.