Help please! I've had my 3GS from new one year now with no problems. Since two weeks ago the phone will ring, I'll only get a single ring, maybe 10 times a day at random times. When I get the single ring the display doesn't illuminate and flash as when I have an incoming call, the screen is blank. The phone is otherwise OK. Now, this is driving me mad. I've pressed the home and on/off button together but this has made no difference. I've checked the alarms and timers and there is nothing shown. Any idea how I can stop these intermittent rings? TIA.