Have you tried using a different web browser, like Internet Explorer or Chrome? It's possible that it's specifically a firefox related issue, in which case I'd recommend reinstalling it and seeing if that helps. You can also try switching to the HTML5 player for youtube using this link; https://www.youtube.com/html5. Just click the blue "Request the HTML5 player" button about halfway down the page, then try watching videos again.
"I think that the problem with this video is it is highly derivative of many popular bands within the genre. Although when viewed on its own merits, it does have a deeper groove. However what it has in groove, it lacks in originality. One can't help but be reminded of such bands as Pearl Jam, White Zombie, Suicidal Tendencies and other bands that bear the mantle of so called "Alternative Rock". One is even reminded of Lorie Anderson when she wore curlers. Hehehmhm! This video speaks less to the heart and more to the sphincter. In closing, I think Korn would do well to learn more from -"