Tried downloading in IE6, IE7, and Mozilla 1.5. Seems that the image hosting company alters the images once they are put up. The background (transparent) layer of the PNG is set as white while the background of the alpha layer is set as black. Unless you didn't save this with transparency enabled. In witch case I know what the problem is and really wish you would post the transparent version

EDIT: I just tried it again, and now the image is fine in all browsers. Something fishy went on earlier, but now I have it just fine