[PNYXPS66]

Make sure the parking brake is not out of adjustment. If the brake cables are too tight, then the caliper will keep the pads against the rotor causing abnormal wear. Also, the heat generated can cause the caliper to actually fuse in this position.

Pull up the parking brake all the way. You should get at least 4-5 clicks out before you feel tension. If you don't your parking brake cable is too tight. Release the brake lever as far down as it will go, to allow as much slack in the cable as possible. Take a hammer (this is tempting I know) and tap (don't swing like a baseball bat) the end of the caliper to get the pad to release. At this point you should be able to move the rear wheel (rotor) freely.

If this is the case, with 21K on the odometer, I'd take the car to FORD and have them readjust the parking brake a little looser and have them replace the rear calipers, rotors, and pads under warranty.

Good luck and I hope this wasn't all babble for you.