This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

gettin this message before it will open: what happened:TypeError: Components.classes['@mozilla.org/extensions/manager;1'] is undefined

  • 2 cavab
  • 27 have this problem
  • 11 views
  • Last reply by TonyE

more options

when I click on mozilla to open my browser I get this message: what happened:TypeError: Components.classes['@mozilla.org/extensions/manager;1'] is undefined then I click OK or close and it starts

when I click on mozilla to open my browser I get this message: what happened:TypeError: Components.classes['@mozilla.org/extensions/manager;1'] is undefined then I click OK or close and it starts

All Replies (2)

more options

Please do the following to update Firefox.

  1. Use Internet Explorer to Download Firefox 4.0.1

  2. When you see the prompt, choose "Save" and save it to your desktop.

  3. Then go to Add/Remove Programs, scroll down to "Mozilla Firefox" and remove it, choosing to keep your bookmarks, customizations etc., (don't checkmark the box).

  4. Then reboot and delete the folder called "Mozilla Firefox" at this location: C:\Program Files\Mozilla Firefox

  5. Finally run the installation file you downloaded to the desktop earlier.


Your bookmarks, customizations etc., are maintained in a different location and will become available to you again once you complete the installation.


I noticed your Flash installation is out of date which potentially exposes your system to exploits. See http://www.adobe.com/support/security/bulletins/apsb11-12.html

Update it via http://get.adobe.com/flashplayer/

more options

That indicates that you are using an add-on that is not compatible with Firefox 4. For details of how to troubleshoot this to find out what one is causing the problem see https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes