From which version did you update?

• In Firefox 3.6 and later on Windows you can hide the "Menu Bar" via "View > Toolbars" or via the right-click context menu on a toolbar.
• Press F10 or press and hold the Alt key down to bring up the "Menu Bar" temporarily.
• Go to "View > Toolbars" or right-click the "Menu Bar" or press Alt+V T to select which toolbars to show or hide (click on an entry to toggle the state).

See:

• Restore the Menu bar in Firefox
• http://kb.mozillazine.org/Toolbar_customization

See also:

• http://kb.mozillazine.org/Lost_bookmarks
• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite

I updated to Mozilla 3.6.1.5 and i have the same problem. I followed the manual removal method to recover bookmarks from here (http://kb.mozillazine.org/Lost_bookmarks_after_Firefox_3_upgrade) , but nothing happened. It's a shame on Firefox that this problem has already appeared from the 3rd edition and is still unsolved. I WILL CHANGE web browser if it's not fixed within a week.