I have a problem with stuttering video on YouTube in full screen. I'm only running YouTube and nothing else.

This video (Elmo Ducks) stutters all the time in 480p:

But, this video (Uncharted 3 Trailer) is silky smooth in 720p and 480p:

Here's the Preware Patches I have installed. I fear one of them is the culprit:
Muffle System Logging
Remove Dropped Packet Logging
Unset CFQ IO Scheduler (maybe this one?)
Unthrottle Download Manager
Govnah (OnDemandTcl1512 @ 1.5 Ghz)

I've tried rebooting a few times, and it always stutters. Does the Elmo video stutter for anyone else? What do you have installed? Thanks for help. It is so frustrating!