FF 6.* fixed .xpi for BK 0.2.2 Rated 5 out of 5 stars
I have found some time to fix the installation .xpi file for myself to support BK up to FF 6.* version but just formally - no binary fixes have been done.
I DO NOT GUARANTEE that this will work for every configuration as Mozilla would wish.
The link for packed content is http://www.filesonic.com/file/1516707924
Just say thanks if it worked for you... ;-)