Comment 24 for bug 220493

Martin,

You're having two problems. First, the unpatched module is being installed by the liveCD. Second, the installer does not support dmraid; so it is not configuring the initrd to load the dmraid module on boot. A liveCD with the module installed would only address the first problem, so you'd still be out of luck. Fortunately you can fix both problems manually with the current liveCD.

To start off, boot up the live CD and run the commands you used on your post to get your raid array started.
Next we want to mount the file system you installed. I'm going to assume that you have your / and /boot on the same partition, if not, make sure you mount /boot as well.

mount /dev/mapper/<your root partition> /mnt

Next we're going to want to switch over to it so we can modify it.

mount --bind /dev /mnt/dev
mount --bind /sys /mnt/sys
mount --bind /proc /mnt/proc
chroot /mnt

Ok, first we'll want to install the patched module so we do it the same way we did it for the liveCD.

cd /lib/modules/2.6.24-16-generic/ubuntu/md
wget http://launchpadlibrarian.net/14473751/dm-raid45.ko

Now we want to configure the initrd so that it loads the module on boot.

apt-get install dmraid initramfs-tools
echo "dm-raid45" >> /etc/initramfs-tools/modules
update-initramfs -u

Now we just need to clean up and reboot

exit
umount /mnt/proc
umount /mnt/sys
umount /mnt/dev
umount /mnt
dmraid -an
init 6

Let us know how this works out for you.