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.

I have also found a single autocompleting hit - however it's a really strange one. When I type "google" I get an autocompleted entry for a google search for google. It I type "googl" or "google." I get nothing. Only with "google" and only that.