I do not know it is a bug for Safari 4 specifically, or general in the page. Or maybe even a usability mis match (=different behaviour then user expects) but:

On page http://www.yubby.com/channel/player/4320/44790 I get a sort of film reel strip on the right side with what appear to be related videos. But when I click on any one of them the currently playing video just restarts. I expect to see a different but related video.