You can try "Reset all user preferences to Firefox defaults" on the Safe mode start window.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode 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

You can check http://kb.mozillazine.org/Locked_or_damaged_places.sqlite

Same problem here. I have Firefox on several machines and OS (XP and Ubuntu [edit: Win 7 too]). However, the bookmarks file is the same in each.

None of the location bars suggest (autocomplete) features work now. I tried deleting the places.sqlite (bookmarks) file and the bar began working again, but all my bookmarks had lost their "favicons". When I replaced that places.sqlite file with my original (including the favicons) the location bar again ceased working.

I highly doubt that the upgrade to 3.6.11 would corrupt every places.sqlite file I have on multiple computers. That leads me to believe that there is some kind of bug in 3.6.11 that messes up the location bar (especially if your bookmarks contain favicons). Hope some kind of patch can be found.

Edit: Just updated Firefox on Windows 7 with same results. I even backed up the places.sqlite (so it could not be corrupted) file before updating then used the backup file when the location bar failed to work. Even restoring with the backup file didn't work - again, this can not be due to a corruption issue.

Finally, I noticed that one (only one) of the autocomplete bookmarks I had selected prior to updating FF in Ubuntu was actually retained. Is there some other file where autocomplete data is held? I wish I knew why that one bookmark is still able autocomplete while all the others will not (note: this is only in the Ubuntu install all other FF installs (in XP/Win7) bookmarks will not autocomplete.

Did you try Safe mode ?

• Make sure that you not run Firefox in Private Browsing - Use Firefox without saving history mode
• In Private Browsing mode some menu items are disabled (grayed) and features like visited links are disabled and not showing
• You are in Private Browsing mode if you see "Tools > Stop Private Browsing", possibly grayed

• You enter Private Browsing mode if you select: Tools > Options > Privacy > History: Firefox will: "Never Remember History"
• To see all History settings, choose: Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
• Uncheck: [ ] "Automatically start Firefox in a private browsing session"

Sorry about the delay - I lost my first response I typed up.

I tried safe mode with the same results (location bar wouldn't work). Here's what I did notice, however:

The history autocomplete wouldn't work either (I made sure I turned off "private browsing"). But I did get it to work by selecting "History" only under the "Privacy" tab of the Options. When I selected "Bookmarks and History" it stopped working again (in safe mode only). I tried it in 'standard' mode and history autocomplete continued to work even if I selected "History and Bookmarks". Nevertheless, bookmarks would not autocomplete.

Right now I don't think it has anything to do with my extensions and everything to do with a problem reading the bookmarks file but have no idea why.

I have to step away for a bit, but will follow up on this post, if I can figure anything out or to try other potential solutions.

For any interested, cor-el and I continued this conversation at this post: https://support.mozilla.com/en-US/questions/759909

(After I downloaded an update to Version 3.6.11 a couple of days ago, the location bar autocomplete function stopped working, and I can't figure out how to turn it back on.)

Please see it for more information on this issue as well as a potential solution I thought of that can be used.

same problem here !