I've read about this problem on forums from 2007, and it seems that Apple never really solved it with firmware updates because now i've got the same problem. Basically, if the silent/ring switch is on "silent" then the phone will behave as if it's randomly being switched back and forth between silent and ring. I'll be looking at the screen, and then the bell icon will appear, as if i've put the switch on "ring" and then the bell icon with the line through it will appear and the phone will vibrate, as if i've switched it to vibrate. During this time I am not touching the switch, which is firmly on "silent." Did anybody ever figure out what this issue is and how to fix it?