Firefox as a browser, only on one particular website. It doesn’t happen anywhere else or on another computer. I’ve reported to Adobe but it won’t fix it, will it? Can I re-install it somehow?

nah, its dying, the html5 strain of thinking is killing it 😀

that said mines doing it too, whats more annoying is it b0rks halfway through videos or starts to stutter

Install the latest version of Flash Player. The well-hidden direct download link is here for the Firefox version.

Assuming everything else is ok (you’ve not got some sort of infection on your PC for instance), there’s not much you can do really.