Sure a bent wheel could do this. Do you have steel wheels or alloys. Not that hard to bend the steelies but if you hit something hard enough to bend the alloys you will know it. If you just had the wheels off to do the brakes I would double check your lug nuts. You should re-tourqe them to make sure the wheel is not simply loose. Be careful though, I recently snaped some of my wheel studs because I applied too much force and they were well worn.
