If you are able to view Flash videos (e.g. at YouTube), but cannot view them if you try to make them full screen, you may have a problem with the Flash player and your video drivers. The following article describes how to work around this problem.

If you are unable to view videos at all, see Video or audio does not play. If you are unable to view Flash content at all, see Using the Flash plugin with Firefox.

Disable hardware acceleration

1. Make sure you are using the latest version of Flash. To check your version and to upgrade, see Adobe's instructions.
2. Navigate to a page that shows a video that you can't view in full screen.
3. Right-clickHold down the Ctrl key while you click on the video player and click Settings... in the context menu. The Adobe Flash Player Settings screen will open.
4. Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel.
5. Remove the check mark from Enable hardware acceleration.
   
   
   
6. Click Close to close the Adobe Flash Player Settings Window.

If this workaround allows you to view full screen videos, you should try to update your video drivers by visiting your video card or computer manufacturer's web page.