1997 Honda Accord 1997 Honda Accord squeaking when letting

Something is squeaking when I let off the brake pedal. It only squeaks once very briefly upon release of the brake pedal. I took it in a couple months ago for the same problem. They put new brake fluid in and cleaned and adjusted the rear brakes. The squeak went away for a couple months. Now it's back. I noticed when the e-brake is on and I press and release the brake pedal, there's no squeak at all. Any suggestions would be greatly appreciated. Thanks!