Aha! The “Good” and “Best” preview are different. They appear as the final video does. Now this is interesting. I make the video track solo, and it shows up as pitch black. A problem with the original media itself?

I don’t know much about codecs, but I can try rendering it in Movie Maker before use in Vegas. That has helped solve other issues for me, like importing a video with no video, only audio.
The original file is an avi, with the following properties:
