528128 – gnome-base/gdm-3.12.2-r1 with x11-drivers/xf86-video-nouveau-1.0.11 - gdm: Failed to give slave programs access to the display. Trying to proceed.

I have here an thinkpad-t410 with NVIDIA GT218M [NVS 3100M], linux 3.17.2-gentoo, xf86-video-nouveau-1.0.11 and gdm-3.12.2-r1. Today gdm stops to work.
If I run 'systemctl start gdm', I see only a black screen, I can switch to the console with CTL-ALT-F1. If try to stop gdm with 'systemctl stop gdm', it fails and the keyboard becomes unusable (CTL-C, Enter, ALT-F1 ALT-F2 ... does not work). Via ssh I see that gdm is still running:

rose@gepard:/home/rose(5)$ ps auwx | grep gdm
root     15159  0.0  0.1 357848  6596 ?        Ssl  15:51   0:00 /usr/sbin/gdm
root     15172  0.0  0.1 219868  6876 ?        Sl   15:51   0:00 gdm-session-worker [pam/gdm-launch-environment]

I thought, that I have seen a "Can't start slave process" messsage, but find them now. 'dmesg | tail' says:

rose@gepard:/home/rose(13)$ dmesg | tail 
[  154.374906] wlan0: associate with 30:46:9a:85:bc:de (try 1/3)
[  154.378039] wlan0: RX AssocResp from 30:46:9a:85:bc:de (capab=0x411 status=0 aid=4)
[  154.389800] wlan0: associated
[  154.390189] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[  518.562523] CPU3: Core temperature above threshold, cpu clock throttled (total events = 1)
[  518.562524] CPU2: Core temperature above threshold, cpu clock throttled (total events = 1)
[  518.563556] CPU2: Core temperature/speed normal
[  518.570068] CPU3: Core temperature/speed normal
[  600.906758] mce: [Hardware Error]: Machine check events logged
[18368.160031] systemd-journald[1658]: File /var/log/journal/46a9a745b6974b0ea360b001ad863973/user-1203.journal corrupted or uncleanly shut down, renaming and replacing.

'journalctl -xn' says:
...

Nov 03 15:52:36 gepard systemd[15199]: Startup finished in 100ms.
-- Subject: System start-up is now complete
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- All system services necessary queued for starting at boot have been
-- successfully started. Note that this does not mean that the machine is
-- now idle as services might still be busy with completing start-up.
-- 
-- Kernel start-up required KERNEL_USEC microseconds.
-- 
-- Initial RAM disk start-up required INITRD_USEC microseconds.
-- 
-- Userspace start-up required 100447 microseconds.
Nov 03 15:52:37 gepard gnome-keyring-daemon[15204]: couldn't connect to dbus session bus: Unable to autolaunch a dbus-daemon wi
Nov 03 15:52:37 gepard gnome-keyring-daemon[15204]: couldn't connect to dbus session bus: Unable to autolaunch a dbus-daemon wi
Nov 03 15:52:51 gepard su[17364]: Successful su for root by rose
Nov 03 15:52:51 gepard su[17364]: + /dev/pts/0 rose:root
Nov 03 15:52:51 gepard su[17364]: pam_unix(su:session): session opened for user root by rose(uid=1203)
Nov 03 15:57:46 gepard gnome-keyring-daemon[391]: couldn't connect to dbus session bus: Unable to autolaunch a dbus-daemon with
Nov 03 15:57:46 gepard gnome-keyring-daemon[391]: couldn't connect to dbus session bus: Unable to autolaunch a dbus-daemon with