Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

That might have been helpful if I hadn't reinstalled the program. Now that Firefox won't install at all, there's no program to trust.

You need to go to your A/V setting and disable it and then reinstall FF again. If that doesn't work you need to completely uninstall FF and delete the Mozilla folder and then disable or uninstall or update your A/V and disable it's active checks and let FF install and see what happens. Otherwise if problems continue then you need to contact your A/V support and ask what is going on.

What is an A/V setting and where do I find it?

A/V = anti-virus.

Many have reported issues using the 64bit Firefox. Install the 32bit version from; Download Firefox For All languages And Systems {web link}