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typeerror: components, classes['@mozilla.org/extensions/manager;1'] is unidefined

cor-el replied
lgipson

when i start beta 4 this error message pops up first

when i start beta 4 this error message pops up first

All Replies (1)

This issue can be caused by an extension that is not working properly.

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

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If that didn't help then delete the files extensions.* (extensions.rdf, extensions.cache, extensions.ini, extensions.sqlite) and compatibility.ini in the Firefox profile folder to reset the extensions registry. New files will be created when required.

See "Corrupt extension files": http://kb.mozillazine.org/Unable_to_install_themes_or_extensions

If you see disabled extensions that are not compatible on the next start in "Tools > Add-ons > Extensions" then right-click that extension and select "Find Updates" to do a compatibility check.