There are many problems with Flash player 11.3 right now. Unfortunately, at this point your best solution is to leave hardware acceleration disabled until Flash 11.4 comes out, then update and try again. I'm sorry I don't have a better answer.

Could you please let me know if leaving hardware acceleration disabled causes problems? What happens when we disable it or enable it? Thanks for the answer by the way :)

I wonder how many thousands of people gave up on FireFox because of that bug ... I switched to Chrome, after years of being a FireFox-fan. And I love it.

Disabling hardware acceleration in Flash settings is the workaround given in the Flash videos won't play full screen article. If it works, the article suggests updating your graphics driver. If you can't do that, it's OK to leave hardware acceleration disabled. This Adobe help page has more information:

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

Quote:

If I have display problems with Flash Player, what should I do?

If you have display problems with Flash Player, such as poor picture quality or slow display times, deselect Enable Hardware Acceleration in the Display panel. This should eliminate hardware or driver compatibility problems with Flash Player. Flash Player then uses software to scale and display the content.

See also:

• http://helpx.adobe.com/flash-player/kb/video-playback-issues.html#main_Solve_video_playback_issues

Thanks for giving the information I needed. :)

So if anybody looking for a solution, there is a new update for Flash Player. Just do it :)