Tap on the large logo on the main screen that looks like a speaker. When it opens, scroll all the way down and you will see Set Ring Tones/Alerts. Tap that, then tap the Instant Messages selection. That will open up 3 choices: Blackberry Messenger Alert, Blackberry Messenger groups, and Blackberry Messenger New Message. Tap the last one, Blackberry Messenger New Message. The next screen will have a lot of options: You will see VIBRATION - make sure it is selected ON and that should solve the problem. Hope this helps you.