I've got a 96 Accord EX. That's discs all around baby!
Just did a brake job on all four tires, flushed the lines with new brake fluid at the same time.

Now about 300 miles later I'll be sitting at a stop light and the pedal will gradually go to the floor and I'll be standing on it to keep the car from moving on me. If I (while holding the handbrake) release the pedal and re-apply preassure it's firm again. Under all other conditions the pedal gives me good resistance and the ABS kicks in just when it should.

The first thing I did was re-bleed the lines, but there was no air in them anyway.

What in the world is wrong?