Please tell me I'm not the only one experiencing this on the iPhone 4. Mine was perfect since day 1, ok I did need a bumper, but since last Friday 'till today I'm getting the message No SIM card installed four to five times a day. I reset it and it works, then again. I take the sim and reinstall and the same. In the middle of a call boom "no sim card installed" Its driving me nuts! Any suggestions?