I am printing from Ubuntu 10.04 to a samba printer on a windows system. The samba printer definition on Ubuntu already has user credentials, so it can access the printer on Windows.

When I print from Firefox, I get a prompt for username and password, but the document prints all the same. What is prompting me? It almost looks like the keyring, but I don't get prompted for anything else.

Edit (8/11/2011)
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Evolution also prompts me for a password. I'd put these into the lpadmin group, but I don't know which user is running