lucasbuck on "Some mp4's not playing"

I've got a couple mp4s on my classroom website and they won't play through Flowplayer. They work find on the computer. Any suggestions on what I'm doing wrong?

Here's a link:
http://adventureeducational.com/gallery/index.php?album=videos&image=quartering.mp4

I have 4 videos, all mp4. 2 play, 2 do not. Thanks for any help!