New Brake Pads Dragging

I just had the brakes redone on my 1987 GL-10 wagon and the calipers sound like they are not releasing all the way after stopping. I took them back to the shop that did them, but they said they couldn't fiquere out what was wrong. They will not make the noise when you first start out, but after they warm up with use, they will make a loud moaning noise (don't know how else to discribe it). I went to another shop and they suggested that I change out the pads from the semi-metallic ones over to a set of softer organic ones. I've put about three hundred miles on the semi-metallic ones, but they don't appear to be wearing down enough for the problem to go away. The shop who did the brakes originally now wants to try replacing the rotors they turned with another set of turned old ones to see if this is the problem, but I don't want to pay for their experimentation (I already had to pay for two timing belt replacements in a month after the belt they replaced broke within three hundred miles of driving. They said it was a bad idler pully that caused it, but you would think them being a Subaru Specialty Shop, they would of caught it the first time.) Anyone out there have any suggestions?