This is getting pretty annoying. Ever since updating to 4.2.1, when I am on a call and have the phone held up to my ear...the phone vibrates for SMS notifications and such. This occurs if the phone is on the silent setting and when the phone is set to ring and vibrate. This is happening on my iPhone 4 and my wife's iPhone 4. For the time being, I shut off the vibrate with ring setting. I restored and tested it before restoring from backup. It still happened with a clean OS install. I then downloaded a new copy of 4.2.1 and it is still doing it. Anybody else notice this wonderful buzzing in your ear?