The cause of this was that my account did not have the 'Administer the system' privilege granted in users-admin. This account was originally created pre-warty, which I don't think had this option. Until a recent update, this account was running fine.
I think this is an upgrade issue. The problem also cannot be resolved manually without resorting to the command line, as users-admin is the supported way of tuning this flag on and users-admin was one of the missing sysadmin tools. So to fix, you need to go to a command line and run 'gksu users-admin', and toggle the privilege on your account. ** Changed in: synaptic (Ubuntu) Status: Needs Info => Unconfirmed -- Synaptic missing from main menu https://launchpad.net/bugs/93279 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs