Uh-huh. You mention transparency maps in your original post too .. a completely transparent character doesn't need 'em. And if the trans map is even slightly not black, you'll get ghosting. And have you tried turning him off, visually, by clicking the 'eye' icons in the Hierarchy editor? Maybe just leave one bit visible for the pre-render bits. Something mid-body would do for your invisible man. Something small and about hip height. Ummmm ...