this is interesting, hopefully this fixes it. let us know if it works for longer. I had it working for a few days after reset and then it started acting out again, so hopefully this will turn out to be a longer fix.UPDATE: I may have fixed the clock.
On a whim I decided to pull the negative terminal on the battery and let it sit overnight. Reconnected this morning, and so far today with several startups/drives the clock is holding the correct time.
Note: I had previously reset to Factory Defaults several times (through the Settings menu). Toggled GPS Sync. Manually set the clock. Nothing else worked.
Perhaps disconnecting the battery cleared some clock memory, or forced the time to be resynced -- who knows. But so far today it's working. And yes I still have GPS nav working fine as well. Hopefully this helps someone else.