The fact that you get mixed results is a little puzzling. Are you using the HTML5 trial of YouTube? If so, perhaps the HTML5 videos are working but the Flash videos are not working.

One thing you might not have tried is disabling the new protected mode in Flash 11.3+, which is incompatible with some add-ons. See this support article from Adobe under the heading "Last Resort" for the steps: Adobe Forums: How do I troubleshoot Flash Player's protected mode for Firefox?

Thanks

after reading your post I tried to disable protected mode , and that did not work.

then I pressed on the HTML5 trial of YouTube link and I found that I'm using it, and there's a button at the end that makes me leave the trial , so I left.

now it works just fine . all videos are working as intended without any problems.

I did not Join the Trial , never did , never been asked to . not sure how I was on the trial on the first place

anyway thank you so much for your help, everything works great now

It's good that YouTube works, but troubling that HTML5 video doesn't work. Hopefully that will be solved down the road if you find a site where they don't offer Flash as a backup.

I was having this same problem on Youtube. Firefox 16.0.2. Flash Player 11.5. Youtube videos would play fine in IE 9, but not in Firefox. I too had gotten added to the HTML5 trial. I left the trial and all are now working just fine. Sounds like a bug in Firefox.

Bill

I also have this same problem. I have a MacBook Pro, and use Safari. This is a brand new issue as I hadn't had this problem before and had no issues playing ANY YT video. Suddenly, (since they changed their look, I noticed) I can only play SOME videos. The rest just show a black box with no video or playback options. I have the most recent flash player, as well.

Thanks for posting that link to the trial! (HTML5 trial of YouTube) It says it's an "Opt In" trial, however, I NEVER opted in to it! But I "Opted OUT!" through your link. NOW videos work again. Geesh! Neither could I find any informational link to this "trial" in YT! Thanks for takin over GOOGLE. Don't you just love the big brother approach to computing?

I just had this problem and found a quick and easy solution.

Turns out, AdBlock Plus was blocking YouTube ads, and thereby blocking YouTube videos.

Go to Tools > Addons > Extensions > Adblock Plus > Options > Filter Preferences > Custom Filters > Exception Rules

Add this exception (exactly as you see it, below!):

@@||youtube.com^$document

Make sure it's "enabled" and try YouTube again. Happy watching!  :-)

Wow! Awesome work, thank you so much!! Been trying to get video to work for a couple hours and about ready to give up, this fixed my problem!! Thank you!

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