1 Right-click in the middle of the on the video you're having issues with
2 Click Settings
3 Click the left-most tab
4 Uncheck the 'Enable hardware acceleration' checkbox to disable hardware acceleration.
5 Refresh the page
and that's it!
For those using Chrome: Go to Settings -> Show Advanced Settings (scroll all the way down and click the text to expand) -> System -> Untick "Use hardware acceleration when available".