Your Firefox bookmarks and browsing history are stored in the Places database file, "places.sqlite".
If there is a problem with this file, it can affect a number of functions related to bookmarks and history,
including the "Import and Backup" features of the Bookmarks Manager. If you have a recent profile
backup you can try replacing the original "places.sqlite" with the backup copy.
If you have no backup or if it doesn't resolve the issue, you can force Firefox to create a new copy of
places.sqlite and rebuild the Places database as follows: (You may wish to export your bookmarks to
an HTML file first, as a precaution.)
1. Close Firefox completely
2. Open the Firefox profile folder
3. Remove or rename all files named "places.sqlite", including "places.sqlite.corrupt" files
and "places.sqlite-journal", if found.
Note: In case there is a problem with the JSON bookmark backups, you may also wish to remove all
"bookmarks-(date).json" files from the bookmarkbackups folder and optionally place a recent copy
or export of bookmarks.html in the Firefox profile folder. (This will result in missing bookmarks
if the Firefox profile folder does not contain a "bookmarks.html" file with current bookmarks.)
When you next start Firefox, "places.sqlite" will be rebuilt; however, you will lose your browsing
history of recently visited pages. Your bookmarks will be automatically restored from the latest
JSON bookmark backup or, if no JSON backup file is found, Firefox will automatically import the
bookmarks from the profile folder bookmarks.html file, if it exists.
