In my case, it turned out to be the mechanism inside the "T" (I do not remember the technical name) where the lock cylinder connects to, broke off. The part (the "T") is not expensive but it is kind of a pain to take it out. The symptom I had was the car was working fine one day. I went to start the car and nothing. The key would turn with ease but, nothing.
It may not be the same problem but, you never kow...
Good luck!
