There is an alternative workaround, which is to temporarily suspend the requirement that all extensions be signed. You can find the steps under #2 in the RoboForm FAQ here:

http://www.roboform.com/faq-mac#ts_ff_43

As long as you keep an eye on what extensions you have running, this is a more secure approach than rolling back to an earlier version of Firefox.

Type about:preferences#advanced<enter> in the address bar.

Under Advanced, Select Update. Check the settings.

I'm again back to blank pages & black video screens, I'm tired to deleting cookies, history, Locking out add ons & plug-ins, reentering my user name, password etc over & over, using tricky keyboard entries or clicks bit the problems keep returning. It's functioning again but for how long? I wish I had never updated FireFox, this update is more trouble than it's worth.

Hi sheilach, I think you meant to post in your thread here: https://support.mozilla.org/questions/1112493