This occurs only in Best Quality because it is recorded at DVD quality where everything is interlaced automatically. Computer playback doesn't do so well when playing back these video clips (i.e. Quicktime, Windows Media Player). One way to help ease this problem is by exporting your videos with a deinterlaced format. Try the VLC media viewers that can help get rid of this problem (google it). In iMovie, if you export through quicktime, it gives you an option (if you dig deep enough) to export as a deinterlaced format. I'm sure other programs like Sony Vegas and Adobe Premiere have options of exporting in deinterlaced format as well. That should help ease the problem for anyone who had the same problem as me. (and if you plan on uploading to youtube, the regularly decreased quality of video should help dissipate the lines as well). Remember, this only helps, it doesn't get rid of them completely.