My problem is basically identical to the following:
Put simply, I have a machine in ubuntu trying to connect to another ubuntu machine via a network in order to use the printer attached. There is no problem printing until I restart the guest machine. Immediately it overwrites the printers.conf file (under /etc/cups/printers.conf).
It always adds the same line:
I stop cups and change it to *#*AuthInfoRequired username,password to comment out the command. Start cups. Works great 'til the next shutdown. Then it gets overwritten again.
Googling indicates it may be GTK problem and not CUPS, but I have found no permanent solution to date.
Any suggestions appreciated ....