can't play back anything, stuck on "loading video"

For example, tried to watch this:

http://xfinitytv.comcast.net/watch/Community/8700597605358573112/111988803979/Basic-Intergluteal-Numismatics/videos

This was working fine for me yesterday, but today cannot watch anything. I have the most up to date version of IE and the playback worked fine for me until yesterday and no changes to browser. Tried logging out and back in with no effect.