Firefox 10 not playing YouTube videos

Question

YouTube

Yes: FireFox build from under Yandex, updated to the latest version. We have: everything is fine as it was, only the problem is that the video on YouTube does not play, and from the account - no, from "VKontakte" - no, from "Google +" - no. The page opens, shows a preview of the video, but the video itself does not. I updated Flash and Shokwave (to a heap simply), there is no result. It plays and everything is perfectly reproduced on Opera and IE.
Question: how to fix this without reinstalling FireFox (bookmarks, panels, add-ons, etc. - it takes a long time to return everything back, but I'm already used to it). Thanks

Answer 1

And if you roll back to the previous version, does it work?

Answer 2

And if you synchronize all the data with the server, put it all the same from the official site, and synchronize it back? I just don’t know how things are with FF, but in chrome, all extensions are synchronized along with the bookmarks.

Answer 3

What add-ons are installed?

Answer 4

RESOLVED!
The Adblock Plus 2.0.3 add-on is to blame.
I'm sorry, not very strong with FireFox - corrected. We start with disabled add-ons, if the problem is solved, we start enabling add-ons one by one and identify the "culprit"
Thanks popopo, for the direction of the search.
CLOSED.