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.
Performing at the Comedy Cove--595 Morris Ave. Springfield NJ reservations 973 376-3840
A recent set
dmax on the radio every Wednesday 7-9 p.m. NYC time. Call in! (661) 449-9340 watsonnwatson.com