A possible cause is a problem with the file places.sqlite that stores the bookmarks and the history.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file
• http://kb.mozillazine.org/Lost_bookmarks

You can also try to repair the places database with this extension:

• https://addons.mozilla.org/firefox/addon/places-maintenance/

Hi there, have you already tried the solutions in Recover lost or missing Bookmarks? If not please check it out. If those instructions don't work, we need to know if your bookmarks are still in a backup file.

Is it possible you ended up in a new profile when you updated? Did you get a message about your profile being in use? This case is also covered in that article.

If nothing helps let us know if your bookmarks are in a backup and what version you upgraded from and if you used the automatic update or if you installed a new version by hand. Also if you have any add-ons installed.