Comment 8 for bug 483130

This seems to work fine for me under natty (I did an upgrade from maverick, not a fresh install).

$ ck-list-sessions
Session1:
        unix-user = '1000'
        realname = 'Paul Donohue'
        seat = 'Seat1'
        session-type = ''
        active = FALSE
        x11-display = ''
        x11-display-device = ''
        display-device = '/dev/tty1'
        remote-host-name = ''
        is-local = TRUE
        on-since = '2011-09-08T13:41:34.171550Z'
        login-session-id = '4294967295'
        idle-since-hint = '2011-09-08T13:42:04.326562Z'
Session2:
        unix-user = '1000'
        realname = 'Paul Donohue'
        seat = 'Seat1'
        session-type = ''
        active = TRUE
        x11-display = ':0'
        x11-display-device = '/dev/tty7'
        display-device = '/dev/tty1'
        remote-host-name = ''
        is-local = TRUE
        on-since = '2011-09-08T13:41:45.813003Z'
        login-session-id = '4294967295'
$

My /etc/pam.d/common-session does not contain pam_loginuid:
/etc/pam.d$ grep -v '^#' common-session

session [default=1] pam_permit.so
session requisite pam_deny.so
session required pam_permit.so
session required pam_unix.so
session optional pam_ck_connector.so nox11
/etc/pam.d$

What does ck-list-sessions show for you after logging in on the terminal (before running startx), and after running startx?