I just got this from another site and thought I would share!
HTC confirmed there is a problem with the battery.
1. Their suggestion is to charge it while on until the light turns green.
2. immediately turn it off and charge it again until it turns green.
3. and once again immediately turn it back on and charge it again till green.
Repeat that process until the on and off charge are both green..
Here is the link to the other thread.
http://androidforums.com/htc-evo-4g/...y-fix-htc.html