You did not include full system information, but I imagine you will have FlashPlayer 11.3 installed, and from the information aside you appear to be using a windows system. Flash Player 11.3 has known problems with Firefox on Windows at present. Try downgrading to FlashPlayer 10.3 or if you wish to risk a less secure version FlashPlayer 11.2

Recent crashes of certain multimedia contents (this includes Youtube videos, certain flash games and other applications) in conjunction with Firefox 13 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!

Last time I had an issue with Adobe software, updating didn't help, but uninstalling then reinstalling did.

"Last time I had an issue with Adobe software, updating didn't help, but uninstalling then reinstalling did."

There are known problems at present with Adobe 11.3, but versions 11.2 and the secure version 10.3 do not have these problems.

If you are suffering from the problems caused by the 11.3 upgrade uninstalling and reinstalling 11.3 is not expected to help.