what version are you using?
By means of the #knoppix irc channel, I was informed that as of 3.8.1 scsi emulation is no longer needed, and in fact prevents drives from mounting.
To fix this problem I had to remove all the lines in the stanzas of /etc/lilo.conf that created scsi emulation, such as scsi=hda scsi=hdb etc.
This fixed the problem for me. Just remember to run 'lilo' after editing lilo.conf to commit the changes.