brake crunching noise 1997 Pontiac Grand Am

I recently had new brake rotors and pads installed (as wll as rear drums) on my 1997 Pontiac Grand Am. Prior to the instalaton I had heard what appeared to be a "crunching" sound. It went away after the new brake partys were installed (or so it seemed) but now it is back periodocically...most usually it seems after the car has sat for a while.
Someone has suggested it might have something to do with the ABS system...
my question is : does that make sense, and, if that is the problem what remedial action should be taken?
thanks....miller When does the noise occur, when applying the brakes or when letting off of the brakes?
Can you determine where the noise is coming from, front, rear or middle of the car?
Have you considered taking the car back to where the brakes were done to have them check out the noise?