Do a clean reinstall and delete the Firefox program before (re)installing a fresh copy of the current Firefox release.

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

• Firefox 29: http://www.mozilla.org/en-US/firefox/all.html

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

• Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

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

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

• It is important to delete the Firefox program 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 personal 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.

Thanks for this, but I am worried about losing personal data. I see the profile folder under Firefox -> browser->defaults->profile but that file doesn't seem current.

Not familiar enough with Uninstall--will there be a clear option there to not remove "personal data" if I try that?

(BTW I see that previous install left a "stub" not a full version: Firefox Setup Stub 29.0.1.exe)

Thanks for this, but I am worried about losing personal data. I see the profile folder under Firefox -> browser->defaults->profile but that file doesn't seem current.

You won't lose any personal data.

 Not familiar enough with Uninstall--will there be a clear option there to not remove "personal data" if I try that? 

Yes, during the install around the second step, it'll have a box that is unselected by default that says "Remove my personal Firefox customizations" or similar. Note from my previous reply at the end

Your bookmarks and other personal 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

 (BTW I see that previous install left a "stub" not a full version: Firefox Setup Stub 29.0.1.exe)

That's the installation file that Firefox uses to install its files from. The stub installer is a 7zip archive used for compressing the size of the installer. Mozilla offers Stubs by default if you download from mozilla.org/firefox/new. Mozilla also offers full installs for people who want the full version for some reason or because the Stub wasn't working properly. The full install along with all the supported languages can be found at http://www.mozilla.org/en-US/firefox/all/

I did the uninstall and it still won't run.

install.log says the install was successful Mozilla Firefox Installation Finished: 2014-05-29 15:27:12

I'll try another reboot but ...

I am on an office machine, normally able to install, but could it be a security issue, that I don't have permission to install?

Still won't run. I tried to install from the Start menu and got an unexpected error with

error code 2324

Did you delete the Firefox program folder and installed Firefox using the full installer?

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

It is possible that your security software (firewall, anti-virus) 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

• https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating

But--still not working. I did add full permissions for FFox in the firewall, and also added full permissions for me as a user.

I have to wait till tomorrow--also hope my IT people will show up.

Didn't want to try this > Did you delete the Firefox program folder and installed Firefox using the full installer? assuming it would mean I'd lose bookmarks, passwords, etc.

It is important to delete the Firefox program 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 personal 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

If you keep having problems then also create a new profile.

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