It could be a number of things. First of all, the project properties might be set to "Interlaced" instead of "Progressive" (Field Order=Progessive, and below that, Deinterlace Method=None - Load the Project into Vegas and click ALT+ENTER to check) , or you could be rendering the video with the "Interlaced" box clicked. What type of video are you rendering to? MPEG? WMV?