Hi,
I do not have rb files, but I converted hundreds of rtf/html/txt files with the librarian and when it acts up restarting it works most of the time; sometimes there are files that do not convert even after restarting (happened with html only), those I had to convert first to rtf.
On the Yahoo group Fictionwise there are people who are very knowledgeable about Ebookwise1150 and its tools so it may be worth asking there too. There is a rb group too on yahoo, but the Fictionwise one is the best for Ebk1150 questions.
http://groups.yahoo.com/group/Fictionwise/
http://groups.yahoo.com/group/reb1100/
Liviu