I didn't have any problem reading it , but it did cut out before the Xorg.0.log was complete.
You could use a LiveCD between boots to back up the various logs, just to contain the output and make it easier to extract/compare. As long as there is a cd/dvd drive handy.
Try booting to the console instead maybe. I'd delete the xdm symlink in one of the runlevels and edit /etc/inittab to reflect that. At least it may give you some lee time to probe about a bit before starting X up.
Again, not being an expert, but ... at console prompt, you could check the /dev directory to see if anything is missing there. And maybe starting X, passing it as a cli to the 'strace' program ... and piping/redirecting the output to a text file as a kind of forensic exercise ' 2>&1 |tee out-file.log' may be revealing.
It can be surprising just how usefull 'strace' can be sometimes, it has been very usefull to me lately for tracing down the obscure font choices some programs insist on defaulting to (grin). Then aliasing those up to something that is more suitable for me.
I'm not sure if X is at fault because it happens somewhere between grub / initiation and the graphical log in greeter.
Good point ... also, you mention it doesn't happen every boot, but does seem to have a consistency ... Could there be a lock file involved. One that isn't being removed on a shutdown, causing X's fail on a subsequent boot, and being removed with the reboot, allowing the next attempt to succeed. That can and does happen. Something to do with the shutdown occuring before the system gets to deal with a polled system request i think, such as deleting a lock file. Another thing to look at could be the way udev is set up if your running that. Which, if it does have a hand in it, it would point to a device file not being created when it should. But that dosen't explain the 'every so many boots' part.
The size limit thing is also curious, strange too that the previw worked but the submission didn't and that you can't view that post as well.
Have you still got a copy of it, what is the actual size.
The FVWM wm -=- www.fvwm.org
Somebody stole my air guitar, It happened just the other day,
But it's ok, 'cause i've got a spare ...