I recently updated my iPhone 4 to iOS 4.3.1. Everything seemed to go fine. However, after I sent my next text message the phone quickly showed the restart screen and then all my old messages were deleted. Thinking it was a fluke I restored to before the update. Everything (except the messages I had sent between the update and restore) showed up again. However, again, as soon as I sent another text, my phone restarted and all the old messages were removed. I'd like to keep my old SMSs on my phone and still be able to send/receive new ones.