Incompatibility Firefox-You Tube, Pandora-Real Payer Convert-Adobe Flash
The only way to allow You Tube videos or listen to Pandora on Firefox is to use Adobe Flash v. 11.2.202.233.
However, using 11.2.202.233, does not allow Real Player to convert You Tube files to MP3 audio only. To do this, the later version is needed, which means You Tube, Pandora and possibly Hulu, will not work.
This is a conundrum that is only up to Firefox to fix.
Opaite Mbohovái (1)
There are some Flash issues in the latest version of Flash (11.3). Unfortunately, there is nothing that the Firefox dev team can do at this point, and we are waiting on a fix from Adobe. These articles contain relevant and up to date information.
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!