Back in October when I bought my first Sprint iPhone tech support suggested I do a restore because of poor battery performance. I did the restore and when the phone rebooted I got an error message saying that the SIM card was invalid and that only authorized SIM cards can be used. About 10 phone calls and 6 trips to Sprint and the Apple store (3 each) a week later I got a new phone. Today I restored my phone because I was having an issue with the volume spontaneously maxing out without any input from me. While using an app I would see the volume window pop up and the indicator go to full volume. The only way to get it off the screen was to press the volume down button. So. I restored and now my SIM is again "invalid". I can't believe it. My frustration level is through the roof right now!