One part rendering in Penguin in 'negative'

I have a model in which one part renders in an inverted wireframe sort of way, in Penguin 2, while all the other parts in the file render correctly. I’ve selbadded, exploded, joined edges, every trick I can think of, and it still refuses to render correctly. If I explode the part, it renders OK. I can’t find any duplicate surfaces, but there must be a glitch of some sort that is interfering with the rendering process. Any ideas on tracking it down? Thanks!