I have a BMW325i (2006) with 40,000 miles.
Yesterday, Sunday, I drove 15 miles to Viera and parked in front of the shop in which I was interested.  I turned off the motor and tried to take the key out, but it wouldn't budge.  The transmission was in PARK and the hand brake was on.  However there was no power anywhere, no lights that usually remain on until the car door is opened, no radio, everthing dead.

I tried to turn the steering wheel ("locked"), tried to push start, wiggled the gear shift, all to no avail.

After calls to AAA (they later called back and said they could not help because I had a BMW, it sounded like an ignition problem and they couldn't get the security code.  I tried BMW Service and also the local BMW in Melbourne, but the service dept. was closed and a representative tried to be helpful.  Finally, almost 2 hours later, sitting in the car with my cellphone, I heard a "ping, ping, ping" and power came on.  I pressed the starter, the car started and I drove back home, with everything behaving normally.

Has anyone else had a similar problem, and what was the eventual outcome?

This just happen to me a couple of days ago. Car appeared to be in park but it actully wasn't. I use the area in front of gearshift to store coins I removed covering around gear and discovered a nickel had fallen into gearshift stopping it from going into it proper position remove coin, removed key.