Daskoff, try sitting on a flat surface, then putting in the clutch (in gear) and waiting for an extended period (30-45sec +). If the car starts to creep then you know you have a leak either in the master or slave cylinders. I can't immediately think of a way to isolate which cylinder it would be, if there is leakage. Lemme think on that one...maybe Winfred or Bill R. have some advice?
Cheers,
Duey