I want to ask for more information. Does it happen in Safe mode?

I am having the same problem. Whether I'm on YouTube or on Facebook; I'll go to full screen to watch a vid on YouTube or if I'm on FB, playing any of the games (Cityville, Farmville, Cafe World, ect), I go to put the game in full screen mode and then the whole screen turns BLACK. I'll need to hit the Esc key on my keyboard to go back to the original screen. And, YES, I have tried to get full screen while in FF Safe Mode.

Why can't I view in FULL SCREEN??? Thanks in advance for help.

Try to disable the hardware acceleration in the Flash Player.

See Flash videos won't play full screen

Flash "Display settings" window:

• http://www.macromedia.com/support/documentation/en/flashplayer/help/help01.html

go to the game you want to play, small screen obviously. right click your mouse on any blank space on the page. a little box will come up that says "settings". uncheck the "enable hardware acceleration" box. Done. You can now go full screen.

go to the game you want to play, small screen obviously. right click your mouse on any blank space on the page. a little box will come up that says "settings". uncheck the "enable hardware acceleration" box. Done. You can now go full screen.

Click here to Solve blank / black screen problem while playing youtube videos in full screen mode by OriginalTips.com ,

http://www.originaltips.com/youtube-black-screen-problem-on-fullscreen-solution-24