My disc brakes squeal a little when I move the wheel backwards. I'm guessing that I have a brake rotor that's slightly out of true, but I don't worry about it, since it doesn't occur while I'm riding. But all the important bits are tight, and I know that my brakes are properly bled.

Are your fork etc., rotor, and brake caliper tight? Never hurts to double-check...especially on a new bike.