It seems that Audio Converter Services in OS X 10.7 has nasty bug: internal state got corrupted if application sets bitrate frequently. Even if bitrate value is the same.
Technical details aside – 1.15 is out and it contains workaround for this bug. Audiobook Binder should not crash now on Lion. New version is available via autoupdate. For those who use App Store build: review will take some time (as always) so I apologize for the inconvenience.