power doorlock noise - 96 Sable

[92sentra]

Does anybody else have this problem. When I open the car doors, there is a loud whine coming from the rear door, and that lock doesn't open. It also makes the same noise when it auto locks at 10 mph. The car is great otherwise, it's just a bit annoying. It's a '96 sable with only 37k miles. Funny thing is, I almost bought a '96 Taurus, and that rear passenger door wouldn't unlock either.