My instructions from Intrepid turned out to be unnecessarily complex in Jaunty (probably was in Intrepid too). I just had to copy the firmware files from the original CD (still have it), moved them now to my home partition, and add the file reference to the /etc/sane.d/snapscan.conf file.

firmware /home/dave/.scanner/prisa/u96v057.bin

All the other instruction seem unnecessary! Yay!