Comment 25 for bug 208405

Have you considered reading the KNOWN-PROBLEMS file in /usr/share/doc/iscan?
In particular the section on: The device is recognised as a scanner but I can't scan.

If memory serves me, Ubuntu uses the same setup as Debian, so you need to be a member of the scanner group. You can check the groups you belong to with the `groups` command.

FTR, the iscan package's postinst (%post for RPMs) works damn hard to get stuff working out-of-the-box according to your distribution's policy. The binary packages, both RPM and .deb, that are released via the AVASYS website are tested on Ubuntu and there is no known problem with scanning as a normal user.