First things you should try are:
Blowing into the little hole on the screw end of the battery to get rid of any juice that might have got in.
Give the screw threads on both the battry and the usb charger a thorough clean with a paper towel. Sometimes dirt can build up and stop the contact, thus stopping the charge. When on charge the light should stay red and go green (or flash between red and green) when the battery is fully charged.
Give those a go and if still no luck you may have a dud battery, in which case i would send an email to
john@intellicig.com explaining the situation and they should replace it for you, as they should last longer than a month....but don't quote me on that!
Hope thats of help
edit: Go idea to have at least 3 batteries for the Evo....even though they last a good 4/5 hours you can then always have one on charge.