[JP Noonan]

My friend had a similar problem where both rear calipers refused to let go. The car sat for a week or so near the beach, so I guess corosion built up. The problem was the arm that comes out of the caliper was stuck. To release them he hit the little arm to free them up(lightly, I can't imagine how expensive it would be to fix them). First look at the caliper that is working, and then see if the stuck one it at the same angle. There are other possibilities like the venting clearence being off, or the cable rusted to the firewall. However try the arm first.