My 2007 SEL AWD is the same way. Here in Nebraska you get all kinds of dirt, salt, snow and crap stuck in the brakes. It usually goes away after a few applications of the brake system.
My wife's 2007 Mazdaspeed sex does it so bad the the rear disc brakes make a load "pop" in the morning when backing out of our garage.
Love my Edge....50K on it now.
cuerovman