When I open Firefox, the browser does not open. Instead I get a small window that says: TypeError: Components.classes[cid] is undefined. How do I fix this?

Question

I tried to uninstall AVG antiviral software, but it did not uninstall. Next, when I try to open Firefox I get a box popup that says:
TypeError: Components.classes[cid] is undefined.
If I click OK in that box, I can then open Firefox.
Also I can no longer update Java.
Help!

Answer 1

Possibly you have "AVG Safe search" extension installed as part of "AVG Free", solution involves reinstalling :AVG Free" without the Link Scanner component see
* http://kb.mozillazine.org/Problematic_extensions
* symptom was noted in https://support.mozilla.com/questions/865877
Other possibilities
* "OneClick YouTube Downloader 1.07" as reported in
*: https://support.mozilla.com/questions/864343
* "Java console" needs to be updated as reported in
*:https://support.mozilla.com/questions/863711]
* "HP Smart Print 1.0" as reported in
*: https://support.mozilla.com/questions/857283
* "McAfee Site Advisor" as noted in (also see Problematic extensions above)
*:https://support.mozilla.com/questions/802381
*a theme After switching to the default theme the JavaScript error doesn't appear. (View > Page Style > No Style or if "Firefox" button use "Alt" first to get to the View menu)
*:https://support.mozilla.com/questions/837840
*various extensions/applications but is 1 year back and Firefox 3.6.6
*:https://support.mozilla.com/questions/729606
If none of the above solve you problem use diagnostic approach...
*: https://support.mozilla.com/questions/837840