Why do I keep having to reenter the SIM code after each iOS update? With my iPhone 5, I've been finding that I keep having to unlock the SIM code every time I update the iOS from one minor release to the next. While this isn't a problem, as I've memorized the code, it is rather annoying.

Is there any way to change this behavior, so that I don't have to keep worrying about this?
Is this a 'SIM PIN'?  If so, go to settings - phone - SIM PIN and turn it to off.