Brake Lockup on 97 Probe GT

I just put brakes on my 97 probe gt. Have been driving it for a few weeks, no problems. Then all of a sudden the brakes or brake locks up, I think it is one of the front brakes or both, and the car is stuck. Let the car sit for a hour or so and it is fine. The ABS light is not on and the sensors have been cleaned. When they lock the pedal becomes hard and is at the top with no play at all. I am stumped as is my mechanic. Please help.