youtube black blocking square

[holt]

Is anyone else encountering this? It happens only with Firefox when going to any youtube user home page; a big black square blocks off most of the page; below is an example, using the sample search word 'wind', but it happens no matter what search word or user name I use:

[holt]

BTW, ever since its last update, seamonkey refuses to show youtube in full screen mode; it only shows small screen or mid-screen theater mode.

[holt]

Is anyone else encountering this? It happens only with Firefox when going to any youtube user home page; a big black square blocks off most of the page; below is an example, using the sample search word 'wind', but it happens no matter what search word or user name I use:

I right-clicked on the big black square, and chose adblock, 'block image', and the black square disappeared and gave me back a normal yt screen.
update: Hmm, nope, still there, my mistake; it thought I was choosing a video and took me to it, was all that happened. If I go to any yt index of videos, the black square still appears.

[4wd]

You wouldn't like to share a bit more info, eg.
Whether you have tried it using Firefox in Safe Mode, (hold down SHIFT while starting Firefox)?
What country you're in?
What version of Firefox?
Whether you're set to use HTML5 or Flash on Youtube?
etc
etc