I'm still thinking just the key.
I know that the ignition switch going bad leads to weird things going on (search 'ignition switch and radio)...just read about this a week or two ago here.
Since this all started with the key...I'd start there (find key!) and just chalk it up to another bmw weirdness.
I'm so depressed. No one wants to come see me in NYC: Sat, Oct. 8, 6 p.m. at Greenwich Village Comedy Club.
Mangofy your E46!