it could just be an unbalanced tire...even if they did balance them. i have bad luck with taking my car in for balancing the tires. i usually go to Sam's Club...well, I used to, when i had my cougar. anyway, they screwed up the balancing on the tires 3 times. and one time i took it to a small shop to have it done and they screwed it up too. maybe they can recheck them. or...you could have a radial pull in one of your tires. i've had that before. either way if you rotate them back like brad suggested you'll be able to figure it out.
