I put a new clutch in my 2001 tiburon and the release fork lever that the slave cylinder hooks onto just flaps around without any resistance and a friend said theres a good chance the throwout bearing popped off and got stuck into the pressure plate and the forks are just free. I took the transmission off just to find the throwout bearing still on the forks, so what could of possibly went wrong? (The flywheel and clutch are in the right way!)
The throw-out bearing fork has some sort of pivot that it has to clamp to in order for the fork to work properly.
Could it be that you disconnected the slave cylinder and allowed air to enter the system? A quick bleed might cure the problem.