Lately, this has been happening to me as well (using Firefox 21). Although, in my case, when I load facebook, my flash player and the plugin container load, and then it freezes, and then I get the Unresponsive Script dialog. This only happens on facebook. Quite irritating

Unfortunately, this is not a Firefox problem. My entire machine locks when I enter the Facebook URL into my navigation window regardless if I use Firefox 21. or IE 9. This is before I even log into FB. Very disturbing and no one at FB seems to give a damn.

That sounds more like a virus or virus protection problem. It might also be some employer-installed filter software. It is probably not Facebook itself.

Here's what worked for me in Windows 7

Delete Firefox Preference Files:

   Click on the Firefox Drop Down Button
   Click "Help"
   Click "Troubleshooting Information"–a new window will open

Under the Application Basics section

   Click on "Show Folder"–it's to the right of "Profile Folder"
   A window with your profile files will open.
   
   Close Firefox

   Locate and delete the prefs.js.moztemp file or user.js or 
   Pref1 file. If you find more than on Pref file, delete them 
   as well.  
   
   You can now close the profile folder and open Firefox.

I am having the same problem and my laptop is brand new. I have everything updated and DO NOT use the facebook app. Honestly i think firefox just finally made a version of itself that i no longer like. Its really annoying trying to do shit and having to either restart the browser or my pc. *smh*

I don't have the Desktop plug-in, but the Facebook news feed is constantly freezing up Firefox. Sometimes it even causes my pointer & desktop to freeze as well.

I think I finally found a solution that works for me. After trying everything in this thread (to no avail) and about 5 other solutions I found online, I closed firefox, uninstalled flash (using the adobe uninstaller) and then deleted all the remaining files in C:\Windows\System32\Macromed\Flash

Haven't had a single hiccup since on facebook or any other website.

Here's a link to the official uninstaller: http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

@Ahni problem is though i need the flash in order to play my fb game potfarm. I really dont play any other games but sometimes watch youtube videos though not often but even youtube needs flash.

the stupid script is really annoying and i dont get it on any other browser, i just really love using firefox. the other browsers all annoy the s*** outta me lol.

This problem has been reported for 3 months now. We still have no satisfactory solution. I might have missed one or two preference files in Firefox.