2005 Toyota Camry All brakes will not release

It started with the front left brake hanging up, I changed the caliper, still hung up. I flushed and bled the system, now all four brakes are hanging up. I have normal braking for about 6 to 7 applications and the brakes begin to stay applied, a little at first, until the car is completely locked up. I need to bleed the fluid out to release the brakes but it starts all over again. I don't know if the master cylinder causes this or the abs brake pump (regulator). How can I tell what part and who would I take this to, (the local brake shop is clueless!) Would a dealer know? I live way out in the sticks and can't afford to waste time and money! Thanks for any help you can give me!