Comment 25 for bug 181242

Hardy Heron 8.04 (alpha 5 to beta) updated
I also get this for my printer: HP Laserjet P1006
$ /usr/lib/cups/backend/hp
direct hp "Unknown" "HP Printer (HPLIP)"

the problem seems to be with libqt3-mt as the file attribute is 640 for one of its files
I have filed this as a separate bug:

$ ls -l /etc/qt3/
total 8
-rw-r----- 1 root root 761 2008-04-10 08:37 qt_plugins_3.3rc
-rw-r--r-- 1 root root 975 2008-01-21 21:01 qtrc

as a normal user:
$ hp-toolbox

HP Linux Imaging and Printing System (ver. 2.8.2)
HP Device Manager ver. 11.0

Copyright (c) 2001-7 Hewlett-Packard Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

QSettings: failed to open file '/etc/qt3/qt_plugins_3.3rc'
error: Unable to communicate with device (code=12): hp:/usb/HP_LaserJet_P1006?serial=AC094VM
warning: Device not found
error: Unable to communicate with device (code=12): hp:/usb/HP_LaserJet_P1006?serial=AC094VM
warning: Device not found

with root priviledges it's normal:
$ gksu hp-toolbox

HP Linux Imaging and Printing System (ver. 2.8.2)
HP Device Manager ver. 11.0

Copyright (c) 2001-7 Hewlett-Packard Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

I filed it as a separate bug for libqt3-mt bug 214962