It appears that an update adding widget_referrer was added to the YouTube API on June 12. The CC no longer shows up for my videos and the language in the settings no longer shows up. It works on YouTube correctly, but not in my iframe tag shown (mostly) below.
iframe frameborder="0" width="640" height="360" src="{{ video.url }}" /iframe
(It's django - the video.url reference works fine.)
I've monkeyed with cc_load_policy, origin, and putting something into the widget_referrer with no success. Any suggestions would be greatly appreciated (for example, I just put http:\mydomain.com as the widge_referrer. Should that have www. in it?)