Youtube videos are choppy but the sound is fine

[19nffc77]

I found in another thread a link to an HTML5 video and a non HTML5 video and played both, the HTML5 video worked fine but the other was choppy. I am using a Macbook pro and Safari and my flash player is v.13,0,0,201. I have also tried checking/ unchecking 'use hardware acceleration' but this doesn't seem to have any effect. It just seems to have started after the latest upgrade. Any help appreciated.

[C_F_McBlob]

Safari>Preferences>Advanced

[19nffc77]

Thanks for the reply Mike. That box is already unchecked.