Revisiting this issue, 05 MKIV. New v31 and nav update and no problem for a few thousand miles. Then, like others, funny little freezes that I could cure at first by switching modes, then only by turning ignition of and on at stop lights, then I needed to eject and re-insert the cd. Finally, nothing worked and it was totally locked no matter what.

The cure? Went to In N Out Burger at a busy time. Gave it that quiet time it needed and worked fine. Good thing I didn't go through the drive-thru lane.

I would guess that this successful reboot indicates that the laser is ok and the aftermart map disk is good, that occasional problems must be inherent and not preventable? Or, am I wrong there?

A reset button would be better, but BMW probably thought that would send the wrong message...