I've been coming across this quite often lately and I figured out that for some reason when a video is embedded in another site there's never a problem with playback.So for example we'll use http://www.youtube.com/watch?v=Eh9XwSgCigc which is not loading for me.

You can share it to your facebook or google+ or you can simply replace the part that says  youtube.com to endlessvideo.com and that will take you to a site that loops videos on YouTube or specific parts of them down to a second in lenght.
As you can see the video loaded.Also you can use that to get around the age verification on youtube if you're at a friends house for example and don't want to log onto your google account.
Hope that helps!