You may find that your pads have not worn evenly (or you may have sanded them back) and when you apply light pressure the full face of the pad isn't touching the rotor so it squeels (this is what I was told by a reputable brake mechanic in sydney). I get a similar noise on very few occassions, if I softly press the pedal I get a gentle squeeze but if I stand on it then it brakes like it should and without squeel.
You may also want to take ur wheel off and make sure the little shims are in place.