Youtube Treating Videos Viewed On Youtube As Embedded Videos-Cannot Play

When I go to watch videos on Youtube in the most recent version of Firefox, the player treats them as though they were embedded; they do not begin playing automatically, there is no option for pop-out, and there is a "Watch this video on Youtube" button in the lower right-hand corner of the UI. Furthermore, when I try to play the video, I get a black screen and " An error occurred. Please try again later." I should stress again that I am ''already'' on Youtube when this is happening. This is not a problem with embedded videos on other sites, this is actual videos on Youtube behaving like embedded videos. I've already cleared the cache and cookies, disabled AdBlock, updated Flash, and updated Firefox; no joy.