While I am assuming you have already check it, I will still suggest you check the battery terminals. I have experienced the no-cranking, no power to anything before and it turned out to be a bad or loose terminal. The looked fine, but when I messed around with them, was when I found out there was a problem.
I will admit that I'm not sure if my suggestion relates to the car turning off suddenly though.
By the way, do you have an electric fuel pump?