There are two things to check

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}

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.

Thanks for reply but I found the solution. Many forum answers suggest changing Network settings but that doesn't work either. The combination that did solve the problem was to run "SuperAntiSpyware" which found virus, that Norton did not block. AND to uninstall and reinstall my copy of Norton 360.

Most anti-virus can't detect mal-ware. Use these once in a while

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

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