Does it work if you boot without X and modprobe nouveau manually? If it does, can you disable page flipping in xorg.conf (Option "PageFlip" "0" in nouveau device section) and recheck with X?
It happens long before X, when the nouveau module is loaded.
Does it work if you disable acceleration (nouveau.noaccel=1 in kernel command line)?
nouveau.noaccel=1 is already on my cmdline as running X with accel enabled never worked anyway.
Is there anything saved in /var/log/ from previous boot? Can you ssh into and check dmesg? Can you use netconsole and catch full log?
Thanks for the netconsole tip. I have attached the log.
I am not an expert but it looks like a crash in the inlined nouveau_software_vblank(). Is the vblank.list already initialized at this point?
Thanks,
Ortwin