Are you sure the problem isn't spokes creaking against each other or in the nipples? Put a drop of oil at each spoke crossing (I assume the wheel isn't radial laced on both sides) and nipple entry and see if that helps. Also try cleaning the dropout faces and tightening the qr skewer a bit more. The creak may be there too.

Bearings normally don't creak when they are dry. They either squeal or make a grinding sound.