SD, perhaps I misunderstood the OPs' original query. I can view Youtube vids directly, no trouble. It's the links to Youtube, such as in PPrune, that is giving me hassle.
I just see a blank space. Certainly I can right click etc to view. I just thought the original query by rans6 had something in common to my issue. It did start with the latest FF upgrade.
Sorry about the posting in multiple threads.