2000 Chrysler Concorde Door Won't Unlock

Thanks in advance for any help. My 2000 Chrysler Concorde's rear right passenger door lock is stuck in the locked position. And, the interior lock lever won't move from the "locked" position when you try to force it with your hand. I've tried warming up the car, to no avail (in case of ice). Can anyone indicate what the problem/solution might be? Thank you.