Power problems with Droid Incredible 2
The Incredible 2 has a defective charging port that does not typically last a long time. It is an extremely common issue with this phone. Chances are, this is what you are seeing.

Disclaimer: I have been using my current dinc2 for ~18 months and haven't had this issue yet, but I did see it on a used phone I attempted to buy. Anyway, my plan for if/when this does happen is:

Repair HTC Incredible 2 USB Charge Port

The part is supposed to be $12 and takes an hour to do. If you're not comfortable doing it yourself, I'd take it to a cell phone repair shop.