My 600 did something really strange a few days ago in the car on the way back from Boise, following a route on CNNA.
I happened to look down at it after it had been performing normally for several hours, and it had gone dark with only the Garmin logo showing. I removed it from the cradle and held the on/off button down for at least 2 minutes.....nothing. Poked the screen a few times.....nothing.
I put it back in the cradle and ignored it for another 15 minutes or so, when it suddenly came back on, not a reboot, but following the road in my actual postion on the map as if nothing had happened at all!
I've had it shut off completely several times, always remedied by a remount in the cradle, which I assume is a battery contact interruption (it could use fresh ear plugs), but this is something totally different. Any ideas?