youtube and sidereel

Hi, I have a new macbook air and when I try to watch a youtube video it wont play it will play one second and freeze then a few more and sometimes will fill with yellow and pink lines, if I try to watch a tv show on sidereel or something it will say the file is loading and if i do it on my old macbook the file works immediately. Ive tried on both safari and firefox and neither works. Any info would be appreciated

Other than suggesting you update your Flash to the latest version, I'm at a loss as to what might be going on there.