Please check if it is a problem of gksu/sudo or synaptic. sudo/gksu is used to give your user root rights - perhaps your alternative authentication system breaks sudo.
Run "sudo -s" in a terminal. This should give you a root terminal. Afterwards run "synaptic". -- Segmentation Fault When Trying to Run Synaptic https://launchpad.net/bugs/56045 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
