Unable to process the backup file - Firefox
From MozillaZine Knowledge Base
Starting in Firefox 3, you can replace your current bookmarks with a backup file using the "Restore" feature of the Bookmarks Manager ("Bookmarks -> Organize Bookmarks -> Import and Backup -> Restore").
Exit Firefox completely (or reboot the computer) and reopen Firefox. If the "Restore" feature now works, a previous Firefox process may not have closed properly. If this is a recurring problem, see this article.   
If you still see the problem, even when you first open Firefox after restarting the computer, the JSON bookmark backup file you are trying to restore may be damaged. Bug fixes in Firefox 3.0.5 have reduced the likeliness of this occurring so make sure you update Firefox if you are using an older version of Firefox 3.   If you are still seeing this problem in Firefox 3.0.5 or later, even in your most recent bookmark backup files, try the following:
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.)
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.  
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