Some time ago I had the same problem with the usr/lib/cups/backend/hp failed error message.
If I remember it correctly, running chmod 755 /usr/lib/cups/backend as root solved the problem for me since the permissions of /usr/lib/cups/backend were to strict. https://answers.launchpad.net/ubuntu/+source/hplip/+question/93468 gave me this workaround. Maybe bug report #587068 results from the same bug. -- To UNSUBSCRIBE, email to debian-bugs-rc-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org