slideattack

So.....

I have a PBM hydro ebrake with a wilwood Master with a reservoir and z32 calipers. The system is completely stand alone and not inline. The brakes lines are all new with no leaks. I just replaced the master, pads and calipers because i thought the there was a problem with the old stuff. I just replaced all of the old harware with the new stuff and Bled the whole system like 6 times. Then i took the car for a spin and it locked up like a champ. The problem is after a few pulls it stays locked and the rear brakes stay engaged. What can be the issue. Its probably something stupid but i cant figure it out...any suggestions?