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When I upgrade my version of Firefox it does not open. I have to revert to Versioln 3.6.3 in order to be able to use Firefox. I have tried dozens of times but a


I cannot install any version of Firefox newer than Version 3.6.3. When I try it will not open. I then have to use Internet Explorer to reload the old version (3.6.3).

Additional System Details

This happened

Every time Firefox opened

This started when...

When I downloaded Version 12.0


  • User Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20110707 Firefox/3.6.19 ( .NET CLR 3.5.30729)

More Information

  • Top 10 Contributor
  • Moderator
2042 solutions 8887 answers

hello, which security software & firewall are you using? in the past we had similar reports that suggest this might be related to malware on the system. please do a full scan of your system with your security software already in place & also use other tools like the free version of malwarebytes and kaspersky's rootkit scanner.

Hasan 477 solutions 5600 answers

-> Uninstall your current Firefox as described in this article -> Uninstall Firefox from your computer

  • Restart your system

-> Download latest Firefox version from the following link using some other Web Browser:

-> Install Firefox 12 as described in this article -> How to download and install Firefox on Windows

Check and tell if its working.

Question owner

I did everything exactly as per your instruction with the same result. Firefox 12 appears to download successfully but it will not open. I had reload version 3.6.3 as it appears to be the only one that works. I did a scan with my McAfee Security but no problems found. I am using Windows XP Pro. Internet Explorer 8.0 works fine but I don't care for it for all of the reasons that Firefox users agree.

  • Top 10 Contributor
  • Moderator
10738 solutions 96600 answers

Did the Firefox installation finish without problems?

You can check:

A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.


Question owner

I uninstalled McAfee to ensure that it was not interfering with the Firefox 12 download. Once the download went smoothly but yet again Firefox will not open. I have reverted to the old faithful Version 3.6.3 as my web browser.