Strange redisplay problems with Xorg 7.4 and intel driver

[Tassilo Horn]

Hi all,

I use Xorg 7.4 with the free intel driver (2.4.2) on a Lenovo/IBM
ThinkPad T61.  For more than a month I suffer from heavy redisplay
problems, for example:

  - I close a window, but it's still displayed.  When I move another
    window over it, it'll be erased.  (It's like cleaning a chalkboard.)

  - I follow a link in a webbrowser, but the old page is still
    displayed.  In order to see the new one, I have to move the window.

  - I compile something in a terminal and some lines are not refreshed.
    Again, moving the window forces a redisplay.

Since the problem occured the first time I've used several versions of
X's components and linux kernels, but the problem still occurs in each X
session.  Unfortunately I don't know what update was the culprit that
caused the problem the first time.

The X logfiles in /var/log/ don't indicate a problem.

What's interesting: Whenever I plug a second monitor and use it with
Xrandr, the problem is gone.  It only occurs when I solely use the
notebooks TFT.

That's really a showstopper for me.  So please could anyone give me some
advice how to debug what's going wrong?

At http://bugs.gentoo.org/show_bug.cgi?id=238041 I filed a bug report
which includes a logfile and my xorg.conf.

Thanks a lot for any pointers,
Tassilo