Recent crashes of certain multimedia contents (this includes Youtube videos, certain flash games and other applications) in conjunction with Firefox are most probably caused by a recent Flash 11.3 update and/or a malfunctioning Real Player browser plugin.

In order to remedy the problem, please perform the steps mentioned in these Knowledge Base articles:

Flash Plugin - Keep it up to date and troubleshoot problems

Adobe Flash plugin has crashed - Prevent it from happening again

Flash 11.3 doesn't load video in Firefox

Other, more technical information about these issues can be found under these Links:

http://forums.adobe.com/thread/1018071?tstart=0

http://blogs.adobe.com/asset/2012/06/inside-flash-player-protected-mode-for-firefox.html

Please tell us if this helped!

I was having this problem and searched everywhere before I found the solution. One of my config settings had somehow got changed and I had to change it back. In url bar type about:config You may be asked if you are sure you want to do this. Click yes. In the search bar, then type in plugin.scan.plid.all If this has been changed to false, then you found your problem. Right click on it and select toggle to change it to true.