I don't know why. I think I noticed a day or so after it actually started to do it...or not do it, rather. I've checked so many settings...It's set to vibrate in the actual settings. I set it to vibrate in handcent. I even turned on the stock messaging app to see if that would vibrate and nothing. I tried holding down end call to see if it would vibrate and nothing. The only time I've felt it vibrate is when powering on the phone. Anyone have any ideas? If not, is there an easy way to restore to factory defaults?