TurboPrint & PrintFab

I have a similar problem on an MP600.

I solved it by checking the permissions of /dev/usb*

Turned out that cupsys runs as user "cupsys", which needs to be in group plugdev. This is on Ubuntu Feisty. So check

ls -l /dev/usb*
ps aux |grep cups
grep plugdev /etc/group

If that is the case for you ...