This is happening on Flash 7 and 8 videos.
Here is a sampe site:
http://www.on2.com/video_samples/flix-video-samples/
Right clicking on the video itself gives mainly access to "About Flash Player 8" and their settings dialog box.
Trying the Page Info I described above saves just the outline of the player-not the contents of the video itself.
I tried Frogza's method and it just wants to save the link as an HTM file; not the actual video.
I'll look into Flash Save but was hoping Mozilla had kept up with Macromedia.