We use the factory navigation alot, including yesterday on a short trip. All of a sudden the map disappeared and the home screen, purple delight, was showing. The Map and Nav buttons did nothing. Everything else kept working - Sirius, etc. Just stopping the car, waiting and restarting didn't help. Then I stopped and turned the music off and pressed the Reset button on the head unit... After a bit the navigation was back in place and working....!? This has the last spring s/w update on it. Checked with the dealer and they said, "sure - trying pressing the reset button!" They are about 3 1/2 weeks out on appointments. Just wanted to report this - first time in 1 1/2 + years...