I want to reiterate that this works.
I recently had to switch out my primary hard drive and restored my entire operating system from a Time Machine backup. When I did so, there were three things that I noticed as a problem:
1. Aperture no longer played videos of any kind (which previously worked)
2. The video thumbnails were just random, glitchy nonsense
3. There was no Mountain Lion recovery partition on my hard drive
I repaired permissions system wide, and then completed all three of the options for Aperture's inspect, repair, rebuild, I reinstalled aperture, nothing helped. I downloaded and ran the Mountain Lion installer and the videos appeared and work perfectly in Aperture.
To fix the funky thumbnails, I filtered all of the pictures to be "File type: video," selected all, and then went to "Photos > Generate Thumbnails." It properly regenerated the thumbs based on the videos.