Comment 58 for bug 283128

There was a recent update to the xserver-core package, which made the problem reappear (because it overrides the patched version paulus provided). I recollected all info from the posts above on how to apply the patch to the latest src and build the package yourself. These are the steps you have to run:

First, 'cd' to a directory where you can safely download the source.
Then

mkdir xserver-xorg-core-src-karmic
cd xserver-xorg-core-src-karmic
apt-src install xserver-xorg-core
wget http://launchpadlibrarian.net/33566768/xserver-xorg-1.6.4.diff
cd xorg-server-1.6.4/xkb
patch -p1 <../../xserver-xorg-1.6.4.diff
cd ../..
sudo dpkg -i xserver-xorg-core_1.6.4-2ubuntu4.1_amd64.deb

Have fun!