Vibrate mode on KRAZR

Quick question for the top peeps from verizon.

I set my phone to vibrate when im at work, i have the setting to vibrate and also found a section under tools that turns vibrate on or off, (which it is on), but yet my phone still doesn't vibrate when i get a call. it just shows the little icon that says im getting a call, all is silent! is my phone defective in the vibration, or am I just not doing something right, i followed the instruction manual but still no dice.

Thanks in advance