Join the Mozilla’s Test Days event from Dec 2–8 to test the new Firefox address bar on Firefox Beta 134 and get a chance to win Mozilla swag vouchers! 🎁

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

After Updating and loading message windw apears "TypeError: Components.classes[cid] is undefined" why and what to do?

  • 2 replies
  • 6 have this problem
  • 1 view
  • Last reply by sergrop

more options

After upgrading to Firefox 6.0 after opening a small message window error opens with the message TypeError: Components.classes[cid] is undefined

After upgrading to Firefox 6.0 after opening a small message window error opens with the message TypeError: Components.classes[cid] is undefined

Chosen solution

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).

Read this answer in context 👍 0

All Replies (2)

more options

Chosen Solution

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 cor-el I solved the problem The offender was "OneClick YouTube Downloader 1.07" I removed it and FireFox works OK