Try downloading the installer and installing Firefox again. Something might have gone wrong with the installation.

• http://www.mozilla.com/en-US/firefox/all.html

Thanks, I did that and Firefox now works properly. I can't figure out why it didn't work before.

I greatly appreciate the help.

I had the exact same problem as swdesertrat , but I tried the link and downloaded it, but it still didn't help me. I just got this computer for my birthday, and I've only had it for a few days now. Firefox was working fine and then on Sunday it decides to not work. Anyone know why not? I need help! I am currently using Explorer, which I don't really like but I can use for now. I have also tried uninstalling and re installing again, didn't work. I've made sure it wasn't running and tried opening it, didn't work. I've tried holding shift while double clicking Firefox, didn't work either.

Help me!!!!!

Which security software (firewall, anti-virus) do you have?

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.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

Try checking in your Downloads file for the .exe Firefox file. Delete that. Then download it again. That's what worked for me. I downloaded through Kim Komando's site. Apparently the .exe file in my Downloads was corrupted. Once I got a new one, no problem.

I have the problem as well. However, when I try to install a new or existing version, or use Mozilla Backup to backup my settings, an error message asks me to close Mozilla. Can't open. Can't modify. Can't backup settings. The computer thinks Firefox is running but it isn't. Shutdown computer: same issue. Thunderbird is fine, however. ???

If there are still problems with an update then uninstall the currently installed version and delete the Firefox program folder to remove any leftover files.

• C:\Program Files\Mozilla Firefox\
• http://kb.mozillazine.org/Installation_directory

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 16.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

problem is, i can't uninstall something that seems to be running (although invisibly)

Can't you delete the Firefox program folder as well?

• (32 bit Windows) C:\Program Files\Mozilla Firefox\
• (64 bit Windows) C:\Program Files (x86)\Mozilla Firefox\

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that works.

This page might help.

• http://kb.mozillazine.org/Profile_in_use