Hmm. Might want to specify your OS and such. I'm on Chrome and Windows 7 and none of those are 404ing for me.
Weird I'm on chrome and windows 7 and I'm actually getting 404's on a lot of videos, its like every other one.
Edit: you know what I think its happening because I'm clicking on the links that people posted on every ER video to quickly get to the next episode, just searched the same episodes and they didn't 404.