I've got the 2.4GHz Intel Core i5 MacBook Pro (base model with 4GB RAM but Hi-Res screen), and ever since I updated to Flash 10.1 I've had very slow performance on many Flash video sites when going fullscreen. I've tried removing and re-installing it, but that hasn't helped. YouTube works fine but on a lot of other sites (including BBC iPlayer in HD, though not the standard resolution) the video stutters/is slowmo fullscreen. For a brief period the problem sometimes goes away, but is more often there than not. It occurs even when I have nothing else running besides Safari. I'm sure that my computer is fast enough - so what could be the problem? Is anyone else having this issue? Any help would be greatly appreciated. edit: oh and also I have the problem on Safari and on FireFox, so it's unlikely to be the browser.