[donv]

To risk the obvious...

I presume your car did not shake before the new tires and you used a shop experienced with high speed balancing. Therefore it is either the tires themselves of something done when they installed the tires. Unless you refused something like balancing or hit something on the way home, then this should all be on their nickel to fix it. I'd just go back to the shop and let them know about the problem - they should be happy to make it right.

Good luck!