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}

Thanks for the reply. I have already done this, I am using Kaspersky internet security. I removed firefox from trusted apps and then added them again. And restarted the device too.

Dump Kapersky -- it's loaded with Russian spy junk, from what I read. I use the free Avast edition. I did have a similar problem. So I blew away and reinstalled FF and an Avast popup added the application to the trusted list. Once Avast gets a clean scan of what you are installing, it almost always adds the program to the trusted list. That's the way it has worked for me...