Could you also check the Library window (Ctrl+Shift+O as in Organizer) to see whether you have any bookmarks there in any of the three categories in the left column? Do you recall any major events happening between the time your bookmarks were visible and when this problem started? For example, Firefox update, Windows update, power off crash, etc. Have you seen the error message described in the title of the following article: [[Fix "The bookmarks and history system will not be functional" error message]]. (If you haven't seen that message, do not follow the steps in that article yet.)