The same EXACT thing happened to me, and I took it in to the verizon store. They replaced the phone, and it still didn't vibrate. An hour or so later, the new droid started vibrating. The tech there didn't know what is going on, and I sure as heck don't know what is going on. But if I were you, i'd try to start safe mode, if it doesn't vibrate in safe mode, take it in. If they can't fix it at the verizon store, they will replace it and hopefully after a little bit your new droid will work fine like mine.
safe mode?
http://www.droidforums.net/forum/droid-hacks/4420-safe-mode-booting.html