Have you tried updating your graphics driver?
Alternately for a quick fix, you can try turning off hardware acceleration. It may not be as smooth but it should get the video working.
1) Right click on video.
2) Click Settings
3) Under Display, UNCHECK the 'Enable hardware acceleration' tickbox.
4) Refesh the page.
In the end, you should try updating your video card drivers, then turn hardware acceleration back on.
Hope that helps.