Bug#633343: xserver-xorg-core: No keyboard after fresh install
A friend of mine had some problem with input devices in xorg. We used a workaround - explicitly configure input devices in xorg.conf: in section ServerFlags disable option AutoEnableDevices and add InputDevice section for keyboard and mouse (the drivers we used were kbd and mouse from xserver-xorg-input-{kbd,mouse} package maybe evdev would work as well).
Without it the only way we found to terminate gdm was using magic SysRq.
I could give you more details if you like, but using xorg.conf like back in the old days should be enought.
I don't see any line like egrep 'Loading.*input' /var/log/Xorg.0.log in your log. I'm quite sure there should be some.
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