I use Firefox 37.0.1, which is currently up to date.
I installed a new plugin into Firefox, then uninstalled it.
I since have a problem with tabs. So I opened about:config and gone to "browser.tabs.insertRelatedAfterCurrent" to correct the problem.
- as expected, this setting is in bold, meaning it is not at the default value (default=true, current value=false)
- a backup of this setting named "browser.tabs.insertRelatedAfterCurrent.backup" is created (with the previous and default value: true)
- I can't switch the setting to true. No message, no error, just nothing when I double-click on it, or with the right-click menu
- the setting is not in italic, and the status column doesn't display "locked"
- I searched for a locking file, and found nothing
- I close Firefox, edit prefs.js to remove the "browser.tabs.insertRelatedAfterCurrent" line. Once Firefox is restarted, the line come back (to the wrong value: false)
- I have the same behaviour into another existing user account, as well as into a new user account. So this is probably something global
- I grepped into "C:\Program Files (x86)\Mozilla Firefox" and found no occurence of "browser.tabs"
- if I create "user.js" into my Firefox user profile directory, with a line setting "browser.tabs.insertRelatedAfterCurrent" to true, it is still false into about:config
- I refreshed Firefox. Same problem
Where can I search to find the origin of this problem ?