It works like a charm - the whole process is driven by a Wizard so easy to use that even raw beginners will be able to set up automatic backups. It also offers encryption of the backup files and a complete push-button restore option.

http://mozbackup.jasnapaka.com/

If you only need to backup Firefox an excellent, perhaps superior, alternative is the free FEBE Firefox extension. Initially designed for backing up extensions it now offers the options of backing up various sections of your profile such as bookmarks, cookies, auto-complete etc. Most importantly, it allows you to backup your entire profile just by checking a single box. Full or selective restore is available. Thanks to site visitor Anupam Shriwatri for the suggestion.FEBE is available from here:

http://customsoftwareconsult.com/extensions/febe/febe.html