you probably mean that the video is interlaced (not deinterlaced). here's a site that describes what interlacing is to help you determine if that's the problem you're having. interlacing will rear its ugly head when interlaced video is viewed on a progressive display, such as a monitor, or a high definition tv where the video is being viewed progressively. if this IS the problem you're describing, there are ways to reencode the video to help eliminate it.

edit: looks like fritzi beat me with the link by a minute.