If your car is not Hydraulic, it could be the clutch cable.

I used to own a nissan sentra and the cable bound up inside the casing. You could push the pedal to the floor and it would not come back up. Maby when they replaced the clutch it free'd up the cable for a little while and now its binding up again. Just a thought.

Of course if it is a hydraulic clutch than this would not be a problem.