This problem appears to arise from a change in a javascript that is used to play the video, and the problem is that your browser may be unaware that it has to reload this javascript. The way to force that to happen is to clear your browser's cache. And the way to do that will depend on what web browser and what operating system you are using. The cache will generally clear itself over time, so this is a problem that fixes itself eventually. Here's how I've obtained a quick fix in various settings:
- Nexus 7 Android tablet: Settings > Apps > Chrome > Clear Cache
- Chrome (Mac OS): Settings (far right of address line) > Advanced Settings ... > Clear Browsing Data > Cached Images and Files
- Firefox (Mac OS): Preferences > Advanced > Network > Cached Web Content > Clear Now
You might try simply restarting your web browser or rebooting this computer. My iPhone was experiencing this problem and cleared up by itself before I could figure out how to clear the cache. So the good news is that this tends to be a self-fixing problem, but the time it might take to self-fix is quite unpredictable. Meanwhile, you have the YouTube versions.
