Comment 6 for bug 874924

is there any consolekit error in your gdm logs or session logs?

the code does

" result = g_dbus_proxy_call_sync (ck_proxy,
                                     "OpenSessionWithParameters",
                                     g_variant_new ("(a(sv))", parameters),
                                     G_DBUS_CALL_FLAGS_NONE,
                                     -1,
                                     NULL,
                                     &error);

    if (error)
        g_warning ("Failed to open CK session: %s", error->message);"

so it seems that for your the "OpenSessionWithParameters" ck call is taking longer than the timeout...