i'm using a windows 7 ultimate full theme, and i've customized one of my app store apps to fit the included icons, but i'm getting a black box around it. i'm think this has something to do with transparency, but i've got all the settings just as i would if i were doing web dev with .png and transparency.

this is my first attempt at modifying any theme elements, so if there's something i should be looking for, let me know.