Sounds like you may have thrown a balancing weight off of one of the two front tires. If you want to check this theory before taking it to the tire shop, swap the front and rear tires on the passenger side and test drive the car. If the vibration is gone the passenger front tire (now rear passenger) was not balanced. If the vibration is still there repeat the process with the drivers side tires. If the vibration is gone the driver side front tire (now rear driver) was not balanced. If the vibration is not gone then you may have to do some more detective work on the front end....

Of course you could always just head back to the tire shop and tell them that the vibration you had before the last balance job has returned.

Good luck

Oliver