As possible hint:
I saw the there where no changes on xserver-xorg-video-intel since January
2009. But the problem occured (as I wrote) about September 24. That may allow
conclude that there must have been a change around that date which belongs to
any sub-dependency of xorg. (This is the very reason because I didn't report a
bug on xserver-xorg-video-intel but on xorg).
It may be worth to know that at this date I attempt to solve another problem.
It was visually the same, but with the difference that the X worked initially
after install and for some reboots. Xorg.0.log did not contain an error (no EE
entry). I was able to solve it by reinstall xorg, gdm and gnome-core by
aptitude but two days later it occured again. Then I completely reinstalled it
which seemed to help. But a day later it happened again that the screen was
black and no error in Xorg.0.log. Then I installed again and got to the point
which this bug report describes.
Taking this two points together it may be possible that the cause is not
necessarily be found in xserver-xorg-video-intel.
