There is still a possibility that the compressor is locked up, and you have a belt that is good and tight with a lot of traction. Have you tried to turn the compressor by hand? Reach down the front of the engine (with the motor off of course
) and try to turn the part of the compressor clutch that is farthest forward, best to do this after the car has been sitting for several hours and is cool.
Test this theory and let us know what you find.