Air in the clutch will cause the inability to release the pressure plate, even though you have your foot pressing the clutch in to the floorboard. (may cause grinding when you try to shift, etc..)
The clutch uses the same system as the brakes, and as such, you should probably bleed the brakes as well, if you have a significant amount of air (enough to be causing problems is REALLY significant).
Same as bleeding a brake system except that when you "pump" the clutch it won't ever get hard like the brakes. just keep pumping, 10-20 times, then hold (even though it is still soft) and have the other person open the valve... let air out (while you are holding, still), then tighten the valve. repeat procedure until fresh fluid flows from the valve, topping off the brake master cylinder as it gets low.
Ray
