Hmmm, actually that's the full XFree86.0.log I have. But now that you mention it, perhaps the log file is incomplete because I "exit" the X start up by pressing ctrl-alt-del to reboot the machine?
Otherwise the screen would remain blank (there's a glitch, it seems like mode switch was done). It's like the X server hangs as the desktop doesn't seems to load (no disk activity at all), there's no cursor and nothing would respond. If the X server crash, I would normally get back to the text mode as I'm in run-level 3.