Comment 7 for bug 368427

OK - so I created a second account on my system, and logged into it, and problems gone [not just sound problems, but flash videos play properly, my browser doesn't hang, I'm able to play 3d games/2d games and not have X or my computer hang]

So try creating a new (second) account (perhaps called "test") and log into it and see if your problems go away. By that point perhaps I what the issue with my profile is...