Sounds like somebody cross-threaded those bad-boys! I bet it was some grease-monkey who didn't know that you were supposed to thread the lugnut on by hand first, before tightening them with the impact wrench.
I watched a guy at WalMart put all four wheels back on a car once by putting the lugnuts in the end of the impact wrench and then threading them on with the wrench. When I asked him if he knew why it was wrong to do that, he said he had been doing it that way for years.
You really only have one option...so you might as well go for it. If they break, like others have said, the studs are easy to replace. Maybe you will get lucky and they won't break. Either way, you have to try.