Voodoo much?

Hey guys,
I am looking for some help on how to use Voodoo with blender 2.57.

I would like to learn how to use blender and voodoo together to composite some scenes of video in my neighborhood with smoke overlaid onto the video. (homes on fire for some simulations).

I have some of the basics down, like how to prep my video for voodoo to accept it (in .tga files), and how to get it back into blender and work with the point clouds and cameras using background video files in the 3d window, but I am getting hung up on the rendering portion. It seems like if I move any scene objects after the first try at rendering a composited animation, my modeled objects then disappear if I try to render again. Am I forgetting to clear a cache somewhere?

Anyway, any help you could give with this would be greatly appreciated.

Thanks,
Mike

sorry if this is the wrong place for this thread, I just saw the majority of other posts related to voodoo were posted here.