Odd that... killing Firefox and restarting does ALWAYS work to stop the halted video thing which I experience. But THAT is NOT what should be needed. I mean even opening a new tab or window and pasting the link in does not allow the video to start...
YouTube has a "spamvelope" code that "watches" and does the forced spam thing, and makes sure they get their pay for wasting folks' time with spam. AND they are now grabbing the mouse cursor to make it harder to hit the skip button, which they move ...