Please peform a clean reinstall, by deleting Firefox from your system, then installing it again. This reinstalls the problem file (one causing the error message). Note: You might want to print these steps or view them in another browser and bookmarks, passwords etc WILL NOT BE LOST.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Mac: Delete Firefox from the Applications folder.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Walka Flocka, thanks for coming to my rescue. I'm concerned deleted the current firefox browser will cause me to lose all my history. And I won't be able to retrieve all my book marks and plugin/extensions, etc. Is that the case?

I did post

"Note: You might want to print these steps or view them in another browser and bookmarks, passwords etc WILL NOT BE LOST."

So nothing regarding your profile will be lost, keeping your data.

You may also, if the clean reinstall doesnt work.

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• On Windows you can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac you can open Firefox 4.0+ in Safe Mode by holding the option key while starting Firefox.
• On Linux you can open Firefox 4.0+ in Safe Mode by quitting Firefox and then going to your Terminal and running: firefox -safe-mode (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

Check for suspicious extensions in Firefox/Tools > Add-ons > Extensions and remove them.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Try to delete the search.json file and possible search-metadata.json and search.sqlite files in the Firefox profile folder to reset the search engines to the default.

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

Firefox will rebuild the search.json file from the default search engines in the "browser\searchplugins" folder in the Firefox program folder and the searchplugins folder in the Firefox profile folder.

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