brucer try this..when you have a issue with a You Tube (or any other site) video...right click somewhere on the playing video and uncheck hardware acceleration. See what that does.
Nope. New driver did not fix it. I will stick with chrome.
i had that flickering issue when i had R9 280x i think the fix was
changing Virtual Super resolution or GOU Scaling.
hardware acceleration is disabled in firefox settings.