Why would a car be stuck in park?

One cause for the key not turning all the way off could be that the tumblers in the ignition lock mechanism are out of alignment. It could be your shift lock control awitch. torque lock. This occurs when you are on a hill and you put your car into park and it rolls back a bit. Use your parking brake! It's there for a reason! Here is a site that will help clear things up: http://www.autoshop101.com/forms/h18.pdf (You must have Adobe Acrobat Reader to view the inforomation.) It is roughly page three that covers the "shift lock release button" and the shift solenoid. If your vehicle is equipped with a "release" or "overide" button then it is almost certain the problem is with the shift lock solenoid. A failing solenoid can be affected by temperature variations. I hope this will help all that reads; it helped me. Philsy