Where did you install Firefox from? Help Mozilla uncover 3rd party websites that offer problematic Firefox installation by taking part in our campaign. There will be swag, and you'll be featured in our blog if you manage to report at least 10 valid reports!

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

I get an error message when trying to open Firefox: load: TypeError: Components.classes['@checkpoint.com/XPCOMTrustCheckerMozilla/TrustCheckerMozilla;1'] is undefined, what can I do?

  • 1 reply
  • 4 have this problem
  • 1 view
  • Last reply by cor-el

more options

This error message has a box with OK in it which I have to press to get Mozilla to open. It is also very slow for the message to come up but opens straight away when the ok button is pressed. Download speeds are very uneven and sometimes it takes a site 5 minutes to open.

This error message has a box with OK in it which I have to press to get Mozilla to open. It is also very slow for the message to come up but opens straight away when the ok button is pressed. Download speeds are very uneven and sometimes it takes a site 5 minutes to open.

All Replies (1)

more options

This issue can be caused by an extension or plugin that isn't working properly.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

  • Don't make any changes on the Safe mode start window.

See:

If it does work in Safe-mode then disable all extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

  • Use "Disable all add-ons" on the Safe mode start window to disable all extensions.
  • Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")