You just replaced the master cylinder, right? (I saw your other thread.) Did you bleed the clutch properly? Usually if you don't bench-bleed the MC, it takes a while to work all the bubbles out of it. Keep bleeding...

The line should be steel except for the short rubber section near the slave. Have someone pump the clutch pedal, then hold it down on the floor. Watch for leaks down there. Watch for the rubber section ballooning up with pressure (it shouldn't). Watch for leaking from the rubber accordion-boot around the slave piston rod.