This is something that is happening to my phone and that I have not noticed before until today. I think it started after updating to iOS 4.2.1. Try this: 1. Make a call (any call works). 2. Look at the iPhone while the call is been connected. 3. The screen blinks lightly while the call is in place. The screen does not go totally off, it is just a "light blink" while the call is in place. The calls sound ok and I have not noticed anything else strange after the iOS update. This blinking happens also when I receive a call. I have tried reseting the iPhone (holding power and the main button) and also reseting it from inside settings. None of these things have fixed the issue. Does your iPhone behave also like this? I am thinking very seriously in asking for warranty here, but I am going to wait after December has passed as I don't want to be without phone during this period. Thanks for posting.