Quoting Andrew Greig (pushin.linux@gmail.com):
Absolutely correct! Machine is an Epson GT7000S for SCSI. The aix scsi drivers are loaded as always. Where I struggle with this one is that this is the first time in 9 years that this scanner has not "just worked" after a new install. I have this niggling thought in the back of my mind that it may be a group membership issue. But what group? And it doesn’t work as root.
Well, come to think of that, the best way of testing (and eliminating) the 'It's a group or ownership issue' hypothesis is to see if it works as root, because then you're wielding root:root authority. However, FWIW, some ways of dealing with permission issues are covered at https://wiki.archlinux.org/index.php/Sane#Permission_problem . 'epson2' is of course the optimal choice of SANE back-ends for your GT-7000S scanner, and there's definitely no need for a firmware blob for it. Have you tried commenting out back-ends other than the desired epson2 one in /etc/sane.d/dll.conf ? For testing purposes, I'd try commenting out all other lines.