Re: After Effects refuses to render my movie.

Try precomposing just your layer with the shadow vertices. Next, open up that precomp and go to Composition>>Pre-Render. If you've never pre-rendered before, what it does is render out the comp you've selected and then AE puts the resulting .mov in the place where the comp was originally. In this case, since you're precomposing the layer with the shadow vertices and pre-rendering it, essentially you're just rendering out that layer. I can't guarantee this will work, but I've had success in similar situations to what you're having.