I have just faced the problem where I got the "Cannot unlock maps" error after a reboot. I had been happily using some extra maps on the SD card when I decided to test out the original maps that came with my unit. After removing my SD card and a reboot the error appeared and has not gone away even after a complete reset. Currently seems to be still working with the extra maps on my SD card but maps on the unit is not showing up anymore.

Anyone with any ideas would be much appreciated. Sounds to me like something got corrupted along the way and I suspect that the traffic subscription isn't working either.