It didn't work for me either:
Using FireFox 10.0.2 and Flash Player 11.1.102.62 (or any other combination that I have tried so far) on Windows 7 64 bit, after a few seconds of playing a YouTube video the video freezes up and after a few more seconds I get the frowny face with the message that Flash Player has crashed. Several people have recommended disabling hardware acceleration but that didn't help. The only way I can get it to play YouTube videos is to go to FireFox Plugins and disable the Shockwave plugin. Now I can play YouTube videos, but some videos that come to me from other platforms pop up with the message: "This plugin is disabled."
I used to be able to play all videos with no problem up to about two weeks ago. I don't want to have to restore to a previous time if I don't have to.
Also, when I use Internet Explorer I have no problems playing either YouTube of those from other sources.
I have seen a lot of questions on this problem but no good answers that have worked for me.
BTW, on each crash I clicked on reload and submit report, but don't know if it goes anywhere.
