Before you do too much work, bear in mind that you won't be able to distribute the result, assuming that was your plan. If you want something to sell or give away you can't use any of M4's geometry. In fact, starting again with a clean mesh will very likely lose the black marks anyway.

If it's for personal use then you can safely ignore me. There are plenty of mesh issues that Poser will balk at, but the folks above me have covered most of them, I think.

If it persists, post a wireframe or similar view.