If xsane have started first time by sudo, the .sane -directory might be owned by root now. And so xsane doesn't find your scanner. Try to delete the .sane -directory in your home folder.
http://ubuntuforums.org/showthread.php?p=1651194#post1651194 -- Epson CX4800 scanner gets "no devices available" https://launchpad.net/bugs/37499 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
