Join us and the lead editor of IRL, Mozilla's multi-award-winning podcast, for a behind-the-scenes look at the pod and to contribute your ideas for the next season, themed: "AI and ME." Mark your calendar and join our Community Call on Wednesday, Aug 7, 17:00–17:45 UTC. See you there!

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

Natao arisiva ity resaka mitohy ity. Mametraha fanontaniana azafady raha mila fanampiana.

Since upgrading to 6 I get "TypeError: Components.classes[cid] is undefined" when loading Firefox - why?

  • 2 valiny
  • 5 manana an'ity olana ity
  • 4 views
  • Valiny farany nomen'i dkjbateman

more options

When loading Firefox or certain pages I get a message box appear with "TypeError: Components.classes[cid] is undefined" if I hit "OK" the system continues. This has only happened since the recent security upgrade to Firefox. I have downloaded Firefox and reinstalled but the message persists.

When loading Firefox or certain pages I get a message box appear with "TypeError: Components.classes[cid] is undefined" if I hit "OK" the system continues. This has only happened since the recent security upgrade to Firefox. I have downloaded Firefox and reinstalled but the message persists.

All Replies (2)

more options

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

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

more options

Thanks traced it to "appearance" switched it to default and problem has gone away.