You may have a problem with the database that stores your bookmarks and history. Try the following.

1. Open your profile folder.
   • Profiles - Where Firefox stores your bookmarks, passwords and other user data
2. Exit Firefox.
3. Create a backup copy of the places.sqlite file.
4. Use the Places Maintenance add-on with the "All" preset.
   • https://addons.mozilla.org/firefox/addon/places-maintenance/

Yes that is where they are stored, but if there is a corruption, is it possible to copy all of the bookmarks in the folder, put it in a new folder and export one more time?

how do you do steps 3 & 4?

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

See also:

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox