Got the same problem since a day: my vibration don't work anymore. What ive found is that there 's still something turning coz i hear a high buzz sound when alarm goes of, but i think the exentric wight that coz the vibration is come loose of it's ax.
Dont hope so coz it means my phone must be send to be repaired...
Damn, so im not the onllyone... Go to my phoneshop and send him for reapair i think. This isnt cool foor an second N900 next the firstone has dead pixles... Bad hardware???