I have the exact same issue, extremely frustrating
and it has been on going now for around 2 weeks, youtube videos won't
load until they fuller buffer in the background. The screen will just
stay black and the loading logo will spin till the entire video has
buffered, then it will start playing. Very annoying.
chrome loads the videos fine (ironic) but firefox does not.
Deleting the cookies/clearing history was a temporary fix before, but it
doesn't seem to work now.
The videos will only play once they
have fully loaded on the grey bar, where as in google chrome they play
instantly, something bugged with the latest firefox version? A solution
would be amazing, I reinstalled/downgraded flash a billion times but it
never fixed it.