well, if anybody is curious, it turns out they *were* related -- apparently the parking brake was totally broken apart and pieces were just tumbling around in there...? hence the squeal...
incidentally, while I was there they pointed out that the front rotors were pretty destroyed.
this is the second time I've had to get the front rotors replaced. both times, I had no warning (grinding sound or anything like that) that the brakes were so worn that they were damaging the rotor. is this a known flaw? shouldn't sometime tip me off that this is happening?