I have no idea why. I keep running into bugs in Mountain Lion. Is it a quality issue? Testing? Coding? But if you have a video in iPhoto (from importing from an iPhone 3GS), and Trim it (double click on video, select "gear" icon and choose "Trim"), your video is now shorter and plays fine in iPhoto. But if you now drag your video outside of iPhoto (like on desktop), the video doesn't play anymore. It is corrupt.
Happens in the latest patches.
iPhoto 9.4.1 (701.67)
OSX Mountain Lion 10.8.2 (12C60)
Happens in the latest patches.
iPhoto 9.4.1 (701.67)
OSX Mountain Lion 10.8.2 (12C60)