my ex auto did that during my audio install...what you can do is keep a spare key in your pocket, or a thin metal object in the car, and put it in the hole by the shifter so you can move the shifter freely, and then put it back in park
what happens is there's 3 switches - if one goes off it won't shift into park like it's supposed to - the lady i bought the car from said it happened to her a few times, and after she drove it to the dealership they took a look and it was fixed and they never could solve the problem
but always keep something in the glove compartment just in case...sucks to have ur keys stuck and ur car not wanting to shut off or turn on lol