Are you using the same program, or did you get a fresh copy at Download Firefox Full Installer For All languages And Systems {web link}

Network Proxy

Type about:preferences<Enter> in the address bar.

Select Advanced > Network. Look for Configure How Firefox Connects and press the Settings button. Check the settings.

Some problems occurs 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}