Whenever I park the car (regardless of how long the trip was) backwards in my driveway (or anywhere else) there's a horrible screaching sound coming from the rear wheels, regardless if brakes are applied or not. Complete silence going forward. Horrible screaching going backwards.

Any ideas? I have CPO so I can have them check it out, but if it something's simple, I can do it rather than drive 60 miles to the dealership.

Went out tonight, it started doing it going forwards, too, under 15mph or so. Started raining, and it's been quiet since then (we'll see when things dry out again). Ideas? Rear wheel bearing?