I'm using Firefox ESR 17.0.6 and I'm having a hard time watching videos on YouTube. So far it hasn't crashed on other sites like Vimeo and such, but then again, I don't use them as often as YouTube. I've had the flash plug-in crash several times at random (complete with the sad-face lego brick-thing) and other times the video won't even load. As in, the Youtube video GUI loads fine and the video doesn't. The buttons seem responsive, but the video still fails to load. I tried waiting for 30 minutes for a 15-minute 480p video to load, thinking I was perhaps impatient, but still nothing.
Everything was installed via the Software Management tool and I have the following repositories enabled: Core Release, Core Updates, Nonfree Release, Nonfree Updates, Tainted Release and Tainted Updates.
EDIT: Forgot to mention that I've tried using it in Konqueror and it seems to work fine there.