I would expect/hope that you inadvertently created a new profile as opposed to removing all previous profile data. * http://kb.mozillazine.org/Lost_bookmarks#Multiple_profiles_and_profile_in_use *http://kb.mozillazine.org/Multiple_profile_files_created Locate your current profile typing '''about:support''' into the location bar, then click on "Open containing folder" which will place you into your current profile. If you go up one directory level you may find additional profiles, check each one to see when it was last updated; files that you can check the dates on include places.sqlite and .json bookmark backup files in the bookmarkbackups folder. If you find that you really should be using a different profile you can use the Profile Manager to change your default folder; otherwise, change your start command, or you could replace the entire content of your current profile with you old profile. It is important that you be able to understand what went wrong and how to correct it. But the first thing to determine is if you are in the wrong profile. You can have only one default browser, and if Firefox is not already open then Firefox would use your default profile by default, and depending on your settings in the profile manager would start it or ask you first. A profile selected via the Profile Manager becomes your default profile.

been there, done that... all profiles contain empty .json files