When you open Firefox it may show error below navigation toolbar with the message’ The bookmarks and history system will not be functional because one of Firefox’s files is in use by another application. Some security software can cause this problem’.

This can happen if you’ve not closed Firefox properly in the last session (power failure and sudden computer shutdown also causes that to happen when browser is open) and damaged places.sqlite file which stores bookmarks and browsing history also could be reason. This can be fixed in two ways.

the bookmarks and system will not be functional

Fixing Firefox’s ‘The bookmarks and history system will not be functional ..’ Error

I. Exit Firefox, restart your computer and open Firefox again, this error may not be showed this time.

II. If restarting your computer hasn’t helped and error is still showing, then places.sqlite file could’ve been damaged. Fix involves creating new places database which isn’t difficult task, here is how that can be done.

1. Open Firefox Profile folder and quit Firefox, find places.sqlite file and rename it to places.sqlite.old, do same for other places.sqlite* files (if exist) too.

places.sqlite file in Firefox profile folder

2. When you open Firefox next time it will create new places database and Firefox automatically restores your bookmarks from most recent backup file (but your browsing history will be lost), if Mozilla’s browser hasn’t done that you can by opening Bookmarks manager>Import and backup>Restore select most recent backup date.