Ok, so I decided to update my "boot knoppix from my partitionless flash drive"
for Knoppix 3.7. IThis works fine on Knoppix 3.6 and seemed like it would be
straightforward; mostly updating my minirt26.gz/linuxrc modification from
/dev/sda to /dev/uba. Lines like:

FOUND_KNOPPIX="/dev/uba"
mount -t vfat -o ro /dev/uba /cdrom

Unfortunately, mount says "invalid argument" during the boot process and fails.
No idea what's going on, since this same mount command works find if I boot
from a CD and mount the flash drive. Any idea how to debug?