If you go to 127.0.0.1:631 in a browser, you should get to the CUPS admin for your printers. Try to do to some pages and you are asked for a password. roots password does not work, which I have enabled. There are some reports googling around with others having the same issue, but no solutions other than to remove the auth directive from the config file.
I would like to know why this is happening, it did not happen a few months ago to me, but i have since done a clean install. I would like to know the correct way to fix it.