[Biker1]

Try a Soft Reset if you haven't already.
This is a Known Issue regarding failing Vibrate Motors.. Covered under WARRANTY. If you are still covered under the Manufacturer's Warranty, Sprint will honor it and give you a replacement. If not, and you have TEP, you are covered. If the answer is NO to any of the above, you can call HTC to see if they can help. First, I would appeal to Sprint and see what they can do for you.
If all of the above fails, you may be able to replace the Motor. See my Signature below for the Link to information regarding Repairs.