Sometimes you will notice that while playing flash videos - such as YouTube videos - in full screen mode, the picture freezes while the audio remains functional. This seems to happen in many browsers such as IE, Firefox, and Google Chrome. What is the problem? How to fix it?
Flash supports something called "Hardware Acceleration". This allows flash to use the power of the video card for rendering high quality videos and so provides a better viewing experience.
According to Adobe, the minimum requirement for the hardware acceleration to work is:
Microsoft® DirectX 9 with VRAM 128 MB for Windows and OpenGL for Apple® Macintosh®, OS X v10.2 or higher. There might be compatibility issues with older hardware and drivers. (See Flash Player system requirements.) With older versions of Flash Player, you should not see dramatic changes as the player reverts from hardware-accelerated scaling back to software scaling.If your system does not meet these minimum requirements, then you will need to turn off the support for hardware acceleration. You can do that by right clicking on the flash video, choose settings, and deselect the "Enable hardware acceleration" check box. This will revert to full software acceleration instead but may cause a drawback in video quality.
For more information on hardware acceleration, visit Adobe's flash player help at this link.