I am using a dual display setup. When I play back a Flash video in Firefox 18 one of my screens shows flickering lines and can only be reset by shutting down and restarting Windows. If I move the Firefox window to the other screen and start playback the main screen still crashes but I can see the video itself playing fine on screen 2. So the Flash plugin didn't crash. But it seems as if it had changed resolution and/or refresh rate to some strange value. So the picture of how the screen looks after the video playback began. Picture: http://www.abload.de/img/distorted_by_flashbful7.png I did no recent changes to the graphics drivers but the problem started about 1-2 weeks ago.