Rated 5 out of 5 stars

I agree 100% with xsandro February 22, 2013
"With firefox 20.0b1 no longer saves the bookmarks HTML and hangs."

and I suspect Ethsen February 25, 2013
"Excellent, been using it for a long time. Just upgraded to version 20b1 and it hangs on extension backups."

is caused by same issue. Under "Backup Type Tab >Selective>Additional options" deselecting "Backup bookmarks (.html)" appears to allow FEBE to backup all other options normally without hanging.

This review is for a previous version of the add-on (7.1.0).