I recently got a Macintosh moved into my room. Everything works fine except when I try to view videos on Youtube. The audio is just fine but the video stutters and skips back and forth even after is is completely loaded. The wierd thing is that when I go on http://www.directlyrics.com which has videos taken off youtube on it, the videos are fine. But there are almost two types of videos on the site and only one works. They are the ones where you cannot change where you are (ex. http://www.directlyrics.com/dirty-money-hello-good-morning-lyrics.html)which work just fine for me or the "regular" youtube videos where you can change where you are (ex. http://www.directlyrics.com/diddydirty-money-perform-on-jonathan-ross--anastacia--dima-bilan-on-muz-tv-awards-news.html) which stutter just like they do on the youtube site though the audio is still fine. Here's some of my computer and browser details:
-Computer: Mac OS X 10.4.11
-Browsers: Safari 4.0.3 (default), Opera 10.61
-Machine name: eMac
If you guys could give me some suggestions as of what to do that would be great.

Have you tried other web browsers? Safari is known for being an all round problematic browser, especially with YouTube.