(And one more in the series... ;-)

This was reported by many people in Ubuntu 10.04, with PolicyKit 0.96 [1]. Seems to happen only with 64 bit archs, and doesn't happen everytime.

Description from one of the reporters:
Clicking on Cancel without entering anything works and closes the window.
Clicking on the Authenticate button with no or wrong password yields "Authentication failure" aka correct behaviour.
If type in the password (which is right) and either hit Enter or click on the Authenticate button, the password input field disappears but the window does not validate nor close itself (when I type a wrong password before the line with "Authentication failure" remains visible).
Clicking on the Cancel nor Authenticate buttons does not work at this stage. Closing the window with the X works as validation.

Several users have the same log:
oem@oem-desktop:~$ pkill -f polkit-gnome-authentication-agent-1
oem@oem-desktop:~$ /usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1

(polkit-gnome-authentication-agent-1:3421): GLib-GObject-WARNING **: cannot register existing type `_PolkitError'

(polkit-gnome-authentication-agent-1:3421): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed


1: https://bugs.launchpad.net/ubuntu/+source/policykit-1-gnome/+bug/445303