Comment 10 for bug 121269

I confirm: Certain youtube videos don't play. They freeze firefox so I have to "force quit" it. As of the latest firefox upgrade no flash file containing audio does work anymore. The browser always freezes! I downgraded to flash plugin version 9.0.31 from 9.0.48 and still the same problem.

There is a bug report in here mentioning it might have something to do with snd_hda_intel. I can confirm that I am having the same sound driver.