Try to disable the hardware acceleration in the Flash Player.

See Flash videos won't play full screen

• http://www.youtube.com/swf_test.html (right-click the player: Settings)

Flash "Display settings" window:

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

Disabling hardware acceleration in Flash should fix this, but the underlying cause for this can be using old video drivers. If you update the video card drivers it may solve this.

Hi. Is there any reason why there are 10 new people reporting this problem this week alone? Just wondering, as it has never affected me before... and I have been running FF in various flavours for many years. Incidentally I have checked for updates for my video driver, and it is the latest NVIDIA one for my machine.

Disabling the hardware acceleration fixed this issue for me. What do we lose in regards to performance when we disable this? I have a really good NVIDIA video card and run 3 monitors without any issues, but when I switched to firefox from chrome today, this green stripe issue popped up. Thanks.

There's a green horizontal stripe across the videos I'm trying to watch, this is happening with the videos require flash Player & Video colors are damaged /Mixed with each other.This is not happening with others like Google Crome & Internet Explorer- Please Clarify - & Same question was put by someone 1 year before then why this has not been sorted out.. Please clarify..

Please try updating your Firefox to 13.0.1, if you haven't already. That fixed it for me. Alternatively, switch off your hardware acceleration (right click on video and go to Settings - uncheck the box)