The problem comes from the combination of Windows x64, latest Flash Player and some ATI video cards, at least that is what I found by searching a bunch of other forums.
In my case, I have a HD7750 on Windows 7 x64, with catalyst 12.10, flash player version 11.5.502.110 and I get the green screen when using Firefox and IE9. I can tell you for sure that it happend as well with the previous flash player version and also with the previous catalyst. I installed the new flash player version (11.5.502.110) with fingers crossed that they might have solved it, but no luck.
Reinstalling Windows also did not help, I just did that a few days ago because I got a new SSD, same story.
Chrome seems to work just fine for me as I am able to watch most of the videos without this issue.
I hope a fix will be provided soon.
And apparently a fix for this issue was already found as I was browsing this Adobe forum, all you need to do is uninstall these 2 windows updates:
KB2735855 and KB2750841.
One of them (KB2750841) appears to be rather useless from my point of view as from it's description: This update improves the performance when you migrate from an IPv4 environment to an IPv6 environment.
These are not security updates and can be uninstalled without any concerns. I have uninstalled them both and marked them as hidden and I currently enjoy watching full HD videos in fullscreen with IE9 and Firefox without any green surprises 
More details here:
http://forums.adobe.com/message/4859584#4859584
and here:
http://www.wilderssecurity.com/showthread.php?t=332920
After fully reading the forum from the second link, I have also found out that these 2 updates are also responsible for corrupting some "*.exe" and "*.zip" downloads in IE9. I remember that some time ago I did not have any issues downloading anything, but then after checking the release & install date of the two updates, I found it clear that this was the cause for the corrupted downloads.
Message was edited by: OrpheusYo