Occassionally this will happen, when some router in between you and the videos has trouble, and you get re-routed somewhere else.

This happened to me last Saturday, so I know exactly what you are talking about.

We are looking into ways we could make this not happen, but as you can imagine, it isn't easy to figure out.

The good news is it will resolve itself in a few days.

Meanwhile, just hit pause and let the video buffer, and then hit play again once you've got some runway.