Well it could be a throwout bearing or broken tangs on the pressure plate. Have you noticed any noise before it broke? Otherwise, I'd say the master/slave just need to be bled. It's a large pain, and usually much easier to replace them as a unit pre-bled from the factory. I had to use a one-man brake bleeding kit, and eventually it worked, but there was still air in it, and after a few days I couldn't take it anymore, so I just replaced the whole set.