As W32.Klez.* the bug i've dicovered has the same strategy. When you create an avatar on Fireworks 4 or an other program with the same abilities. It gives you the opportunity to make a pop-up menu. Its option of this menu is connected with a link. If a bad guy put a button to be connected with a file (virus) with some option it could be a perfect virus. I've tried to make a pop-up menu and i discovered that only PNG file can give that ability in only one file.