Printers/Users Unlock button in settings disabled
Solution 1:
Does not exactly cover the problem of this question (disabled unlock button with no obvious way to enable) but for the purposes of adding/deleting/renaming a printer, you could do
me$ sudo su
root$ system-config-printer
(I believe you can straight-up sudo system-config-printer but something in my machine made that not work.)
From the dialog that opens you can right click on existing printers to delete or rename them.