I have a 2008 Tahoe with 54k miles. I'm having essentially the same issue as everyone else: Nav keeps changing zone from SW to NE ( I live in Az). And when this happens the clock advances two hours. In addition some of the settings change for the radio, for example "Limit Features While Driving" keeps resetting to "ON" when I've set it to off. I suspect other things are resting as well but i haven't discovered them yet. Oddly the radio stations are not changing. I did have a battery replaced about 2 months ago and do not recall having any of these issues prior to that. Anyone have any ideas? thanks