Turns out the update I got today also fixed Google Docs. Could be because I'd disabled flash 10.1 and enabled 10.2 (why the old is still there I dunno, but it is.) Also disabling Flash 10.1 sped up youtube playback plus super mario crossover and mechquest work again.
Type in 'about:plugins' in the omnibar. Click show details. You'll get options to disable individual plugin components. Here's a screenshot that should help.