On my 2002 X5 with Nav and w/o DSP, almost evertime I shut off the vehicle, when I start it back up the previously set radio station is gone. For example, if I am listening to AM 680 it will reset to AM 530 when I return to the vehicle and turn on the ignition. FM resets to 87.7. None of the presets are disturbed, only the staion currently being listened to.

I only use one key, by the way.