I have an iphone 4 with the latest software update. The last couple of times I've received an incoming call, I swipe my finger across the screen to unlock while the phone is ringing. The screen updates to show the connected call, but the speaker keeps repeating a couple of seconds of the ringtone over and over again (I am using the default ringtone). It's in some kind of stuttering loop. This makes it impossible to hear or be heard by the caller. If I toggle to speakerphone, the noise stops, and I can toggle the speakerphone off and the call is as normal. The only thing I have changed recently on my phone is turning on the bluetooth (I bought a BT headset). But this problem happens even when I'm not using the headset. This is a wierd problem. Has anyone else experienced it?