My new iPhone 4 quit ringing and sending out text alerts today and would vibrate only. I went in and checked the sound settings, made sure the speakers were working, and tried changing ringers and I could hear them. I ended up doing a restore and re-sync, fussing the entire time thinking that there was a major problem. With all the reported problems, I knew for sure I had another issue to add to everyone's list. Two hours later a bulb went off in my head....the switch on the side was flipped. DUH!