the utube speed control

[Donn]

This feature can be occasionally useful if you're trying to transcribe something from a video, and it goes by too fast to pick up.

You're looking for the menu invoked from a sort of 6-tooth cog thing (settings) in the bar below the video window. I vaguely remember something about this working only with HTML5 video presentation, not Flash. If that's the problem, you may be able to force HTML5 presentation, http://www.youtube.com/html5.