I've had this same issue, but only on 3 separate days. The Nav is frozen in the spot where the truck is turned on and the icon is blinking. Then if you go into reverse and back to drive or park the screen will be black. I did not know about the trick with the lights or the locator so I will use those if it happens again. Hopefully an update comes out like they say it will. I like using the built in Nav and it would be annoying if it went out on a road trip or something like that.