Maxima Forums - Clutch Problem?? HELP!!

I have a 95 SE.....I recently started having shifting problems were the car would not go in gear with the clutch pressed to the floor with the car on. With the car off gears go in with the clutch being pressed or de-pressed...as soon as you start the car and try to put it in gear...NADA....I changed the slave and master cylinder 1 week ago since they were bad (Mechanic changed them) and he also said that I had air in the Clutch Hydraulic system because of a slightly open bleed valve. Ok...so...the car worked for about a week on a new slave and master cylinder....now the same symptoms are back....with me being furious andf eeling like I wasted $250 on changing a slave and a master cylinder that maybe were not bad. What is the deal...I really believe that my clutch is the one that is bad....and the mechanic said that if it is it will cost me $600 installed. Any one have any other ideas on what could be wrong? I appreciate all the help fellas.