What can it be!?
If it does not then you need to at least see if you can manage to see the slave push in and out on the pressure plate.
If its pulling the pressure off the disc then there could be a prob with the clutch, the pilot bearing could also be froze on the end of the input shaft.
If you see the pressure plate moving off the disc but the disc looks like its bending to stay in contact with the pressure plate and flywheel then the disc is bent.
The friction material can also come off the disc and be stuck to the pressure plate and flywheel, had that happen this weekend to a brand new clutch disc causing it to not disengage.
Car off, put the car in gear, push clutch in and see if someone from behind can push the car. If the clutch material was "stuck" to the pressure plate/flywheel, it may just be enough force to unjam it and get it free spinning.


