said by mattmag:It really isn't so much that you cross-threaded it, but in reality it is almost always a piece of debris that went on along with the nut. One more common thing that gets stuck is a small piece of the threads themselves, which makes for a real nice mess when you try to back it off and the piece gets stuck in the nut. It rips up the threads when enough force is used to back off the nut.
Yes, I'm thinking that is what happened in my case.
My mechanic charged me a total of $41 for the repair, which includes 1/2 hour of labor and tax.