When I'm typing on my keypad, I have my phone set so that when I tap on the screen.it acknowledges it by vibrating. But recently I have been typing or navigating my phone, and suddenly the vibrations stop. This goes on for a while, and then the vibration will come back randomly. It won't even vibrate for any messages.received (SMS, MMS, etc.). Any thoughts on what could be wrong? Or should I just take it to the store to be looked at?