Extension signing is in effect in Firefox 41 Beta. https://blog.mozilla.org/addons/2015/02/10/extension-signing-safer-experience/ https://wiki.mozilla.org/Addons/Extension_Signing

• Firefox 40: Firefox warns about signatures but doesn't enforce them.
• Firefox 41: Firefox will have a preference that allows signature enforcement to be disabled (xpinstall.signatures.required in about:config).
• Firefox 42: Release and Beta versions of Firefox will not allow unsigned extensions to be installed, with no override.

Revert to the Firefox 40.0.2 Release version and those extensions probably won't be disabled.

Can I revert by just installing 40.0.2? Will install over the beta version that I have installed now or will I have two separate programs?

I think the release can take over the profile folder from beta. But it never hurts to make a backup: Back up and restore information in Firefox profiles.

Now... I can't help noticing in your Question Details > More System Details that you have a large number of Shockwave Flash plugins that Firefox detects and this could cause some instability. To track them down and disk and remove them, you can type or paste about:plugins in the address bar and press Enter. You can use Find (Ctrl+f) to look for npswf to jump to the various sections for Flash where the path on disk will be listed.

There are other things that need attention.

Note that your System Details List shows six Flash plugins.

1. Shockwave Flash 11.9 r900
2. Shockwave Flash 12.0 r0
3. Shockwave Flash 13.0 r0
4. Shockwave Flash 16.0 r0
5. Shockwave Flash 17.0 r0
6. Shockwave Flash 18.0 r0

You can find the installation path of all plugins on the about:plugins page.

• http://kb.mozillazine.org/Issues_related_to_plugins#Identifying_installed_plugins

You can check the Flash player installation folder for multiple Flash player plugins and remove older version(s) of the plugin (NPSWF32) and possibly (re)install the latest Flash player.

• (32 bit Windows) C:\Windows\System32\Macromed\Flash\
• (64 bit Windows) C:\Windows\SysWOW64\Macromed\Flash\

Thanks a lot cor-el!