Flash causing problems with Youtube audio

Flash seems to be causing glitches with the audio in Youtube videos. I tried completely uninstalling the Flash player and that fixed the problem. Then I reinstalled Flash, but deactivated it, and that fixed the problem as well. But if I activate it the problem returns. I just can't have Flash active and play HTML5 videos without audio problems. This happens on both Firefox and Chrome. FYI, I'm currently using Firefox with hardware acceleration. Tried reinstalling Firefox, but that made no difference.

I need flash for Pandora, otherwise I'd just ditch it. So, any ideas about how to fix this?

Thanks