Please check this : https://support.mozilla.org/en-US/kb/firefox-wont-start-find-solutions

If return please list your Extensions & AV/Firewall Programs.

Please let us know if this solved your issue or if need further assistance.

Thank you for your reply. I have tried all the recommended fixes from Mozilla but none appear to have fixed the problem. I tried to change my profile to see if this would work but it was to difficult for my knowledge. I am using Norton as my Firewall and in addition a firewall operated by my internet provider. All worked together for the past year but suddenly this problem arose.

Let’s do a full clean re-install; Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them. Do not rename the Mozilla Thunderbird folder if there is one.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. If all goes well, remove the OLD folders when you are done. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

Thanks for your reply. In the end a reinstall fixed the problem.

Thanks for your reply. A reinstall fixed the problem.

Glad to help. Safe Surfing.