A green screen usually means that there is a DirectShow problem with creating the overlay window with the player.

If it is only with Flash then try to disable 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

Seems that problem is back with Firefox 11.0.

"If it is only with Flash then try to disable hardware acceleration in the Flash player." That doesn't make it work here. Flash has been updated to the latest version, but still the same issue. Still that green overlay.

Anyone found a solution yet? This occurs on Facebook with videos made with an iPhone and in some cases it happens randomly.

I found the problem, and I don't think it is with Firefox or Adobe. I have Radeon Graphics running on a Intel Core i7 computer and I was able to solve this problem by opening the Catalyst Control Center and clicking on one setting and applying.

Open your Catalyst Control Center (it may be an icon on your desktop, in the start menu, or accessed via right clicking the desktop and selecting "Graphics Properties") and click on the "power" icon. From there you select "Switchable Graphics", and there should be an area for "recent applications". If you do not see any recent applications, I would re-download the flash player, access a website that uses it, and then retry the above instructions. There should be a "button" to the right of the Flash Player Application and select it until it says "power saving" and select apply. I also tried using "high performance" as a setting and the green screen remained. I am using Catalyst Control Center version 2011.1205.2215.39827, and cannot say if the above instructions will work with any other version.

I am having a similar issue (green screen when playing videos on youtube or on cnn it's black and audio is choppy) and don't know how to fix it. I have Windows 7 intel core i7 processor, AMD Radeon HD 6670 Graphics card. I opened up the Catalyst Control center and there is no "Power" icon or "Switchable Graphics". I have the current version of Adobe Flash Player. I am very frustrated because nothing online is helping me.

Nevermind! I went to adobe webpage. Follow these steps to disable the hardware acceleration!

http://forums.adobe.com/thread/891337