Comment 11 for bug 485551

I performed the same operations as Lucien.

Here is the sequence of events I did and it worked for me.

0) Unplug the scanner from the USB port

1) Uninstall libsane (and dependant libraries) including configuration files
$ sudo apt-get purge hpijs hplip sane-utils xsane xsane-common libsane

2) Install the old version
a) Open http://packages.ubuntu.com/en/jaunty/libsane and install the package for your architecture (libsane_1.0.19-23ubuntu7_i386 for i386)
b) You might want to "lock the version" of the libsane package, so it does not attempt to upgrade it
Find libsane in Synaptic, select it, click on the Package menu and tick "Lock Version"

3) Install back the dependant packages (the current ones, not the old ones from jaunty)
$ sudo apt-get install hpijs hplip sane-utils xsane xsane-common

4) Edit the config file
$ sudo gedit /lib/udev/rules.d/50-udev-default.rules

Find the text
 # libusb device nodes
 SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", MODE="0664"
and change MODE="0664" to "0666"

On my copy of the file, this it's on line 58.

5) Plug-in the scanner

6) Everything should work now.

BTW: For me the change of the mode of the device was crucial. With the original Karmic (9.10) version of libsane (libsane-1.0.20-4ubuntu3) the scanner could be accessed by a normal user. This is not the case with the downgraded libsane.

user1@hp311:~$ scanimage -L
device `v4l:/dev/video0' is a Noname HP Webcam-50 virtual device

user1@hp311:~$ sudo scanimage -L
[sudo] password for user1:
device `v4l:/dev/video0' is a Noname HP Webcam-50 virtual device
device `genesys:libusb:002:010' is a Canon LiDE 35/40/50 flatbed scanner

I then followed step 4 and all was good after that. scanimage -L did show the scanner for a non-privileged user