Last week, I could not remove the key from my 99 SLK230 automatic transmission. All of the stomping on the brakes, turning the key on/off, wiggling the steering wheel did work. I finally decided to disconnect the battery, lock the car up with my wife's key and leave it parked that way. When I disconnected the battery, the key came right out. It has worked perfectly ever since.

I always thought the transmission interlock was mechanical. Is it? Is there some type of electrical interlock that might have failed? If so, does something get reset when the battery is disconnected?