[tlug] "Password on localhost"

[Brian Chandler <brian@example.com>]

I'm trying to set up a printer on my LAN, with Ubuntu, of which I have 
very limited experience. I have a user, brian, with password, let's say 
"password". Generally to do rooty-admin things, I get prompted, enter 
"password", and it lets me a superuser (or whatever).

But when I try things to do with printer/network settings I get a prompt 
which says something slightly different:

Password for brian on localhost?

And typing "password" doesn't work. (Yes, I've tried 4 or 5 times, on at 
least two separate days.)

What exactly does 'localhost' mean here, and how would I find my 
password for it?

I feel I must have missed something very elementary, but I'd be grateful 
for a pointer to it...

Brian Chandler