Wow, how weird. I just went through the same thing last week w/my tetnus shot. It is a new formula. I wonder if that is why so many people are reacting to it?
I had a lot of arm pain after a Tetanus shot once, it was the only shot that ever caused me any pain post-injection. It was soreness and I basically had to not use my arm for about a day and a half. That was two times ago, this last time I had no trouble what so ever.