Had the same thing too, drivers side rear causing a very warm wheel.
Cured mine yesterday by pulling out the outer most pad, bolt caliper back on minus pad then put a screw driver shaft or small spanner through the top to take the place of the pad(Basically to prevent the piston going to far) then pump the brake pedal to extend the piston cleaning up the seal and any crusty crap off the piston while its fairly well extended.
Push piston back in and repeat a few times.
Make sure the sliders are free to move first as they cause the same problem.
Done this a few times with various cars now and usually never see the problem again unless the seal is split around the piston.
Mine was caused by the pads wearing abit low.