What is the possible cause for the front brake rotors to get hot & start to stick?

Hey Pat, I tried to push the caliper piston in, while putting on the the rotor...it wouldn't budge... figured it was because of the pressure of the brake fluid on it... shouldn't that retreat when pushed in? I also was told the the "block" that the fluid goes to the separate wheels might clog..what do you think? I hate just 'throwing parts' at this! It can get expensive doing that..... UPDATE ON 8/24/2010 The caliper piston was fine, Found out it was a break line that had got clogged up.... wouldn't return the fluid to the Master Cylinder... replaced the line and doing well... I try to update these as I get them repaired so future readers might get an idea of what to look for in such matters.

look at update on 8/24, that fixed it thanks for lookin anyway!