[i946gz] Kubuntu: Random garbage appears on old windows

Here's a screenshot. This was after fiddling with desktop effects settings; when I switched back to Konqueror I noticed the window was corrupted.

Then it happened again in the same session, just from alt+tabbing between Konqueror and firefox. This time, I'd disabled desktop effects earlier, because they're really too slow and therefore get in my way. So it can happen regardless of whether desktop effects are disabled or enabled.

$ lspci -nn | grep VGA
00:02.0 VGA compatible controller [0300]: Intel Corporation 82946GZ/GL Integrated Graphics Controller [8086:2972] (rev 02)

Can you please run this command:
apport-collect 373161
(it will automatically attach more detailed information about your hw / sw config)

Architecture: i386
DistroRelease: Ubuntu 9.04
Package: xserver-xorg-video-intel 2:2.6.3-0ubuntu9
PackageArchitecture: i386
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_GB.UTF-8
 LANGUAGE=
ProcVersion: Linux version 2.6.28-11-generic (buildd@palmer) (gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) ) #42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009
Uname: Linux 2.6.28-11-generic i686
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
XorgConf:

Thanks Martin. I've since bookmarked "https://wiki.ubuntu.com/X/Reporting" so in future I'll be able to remember to start off with "ubuntu-bug -p xorg". I've seen it before, but somehow it's never easy to find the right Wiki page at the time you need it :-).

[This is an automatic notification.]

A new major version of the -intel driver is now available in Karmic.

This version includes a major reworking of the acceleration
architecture, which resolves a huge number of issues. We do not know
whether it resolves the issue you reported.

Would you mind testing Karmic Alpha-2 and seeing if it is still a
problem? CD ISO images are available here:

  http://cdimages.ubuntu.com/releases/karmic/

If the issue can still be reproduced on karmic, please report here with
your findings, and attach a fresh Xorg.0.log from your test, and we will
be able to forward the bug upstream.

Otherwise, if the bug no longer exists in Karmic, let us know that as
well.

In the off chance you encounter different bugs while attempting to test
Karmic, please report those as new bug reports.

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.

It seems likely to me this bug is gone; the -intel driver has improved immensely in Karmic and a lot of bugs are being reported as no longer present. So hopefully that's the case here too.