Canon Pixma Ip1800 cannot be configured with CUPS

This is my first email in the mailing lists, I hope this email is in the right place.

Printer: Canon Pixma Ip1800
Driver: PPD file  from Canon driver, cnj filter ver. 2.70

When I try to add the printer using http://localhost:631/ I give all the information.
When asked for my username and password, I type my root password and the username with which I log in to my system.
These wouldn't work, so I typed the username and password which I registered at cups.org with, but no sucess.

The result from
lppasswd -g sys -a root
is "Permission denied".
What do I have to do next?