Some weird technical glitch with some HD vids

I noticed today that some of the videos I'm posting will not play their HD versions on Youtube. They are glitchy. For example: http://www.youtube.com/watch?v=AW4TgOLiF0k&safety_mode=true&persist_safety_mode=1

The lower-def versions are working well, but not the HD. Have not been able to figure out why yet...doh.

The good news is that all the videos still work when played through teachertechvids.com. They're only glitchy when playing directly from Youtube. Go figure. If you have any ideas as to why, please share!

-Steve