Video not playing, shows green screen

I know this reply is incredibly late, but assuming you don't want every user to have to disable their flash "hardware acceleration" just to view your video... I found that moving the video to start with a 1 second delay, it'll make the green screen go away much sooner (within a second or so). I gather It's some sort of buffering issue that happens when the video is a little long. (mine are about 10 mins each).

I ended up starting each video with an image on the top layer, but fading out after a couple seconds, that way it gives the video a second to buffer and the user won't see a green screen. Hope that helps!