after kernel upgrade to generic 3.5.0-27 in Ubuntu 12.10, my scanner stopped working. Xsane could not find scanner.
After reading and checking I found that there is problem with permissions of regular user.

Check if scanner is visible to the system user@user: lsusb

then check correct bus number

ls -l /dev/bus/usb/002

sane-find-scanner gave info that ther no enough permission to access USB

when running sudo sane-find-scanner it was ok.

Install Users and groups tool sudo apt-get install gnome-system-tools

Details http://askubuntu.com/questions/66718...ers-and-groups

Then Run users and groups form main panel then click on Manage Groups

I have added user to grups plugdev and scanner.

Everything started working as usual.

I hope that my post will help someone