Finally got an Update of my OX installation from 8.04 to 10.04 Ubuntu working.
While on the progress and the weather outside sucks anyway, I also updated to newest OX 6.18

0. (If you run Ubuntu in a virtual machine, its a good idea to make a snapshot first.)

1. update ox to 6.18 with
apt-get update
followed by
apt-get distro-update

1a. If apt-get complains about missing keys read http://www.open-xchange.com/forum/showthread.php?t=4797

3. After reboot OX login screens complained about missing javascript, go and change your Apache /etc/apache2/sites-enabled/000-default file
(details here: http://oxpedia.org/wiki/index.php?ti...for_Debian_5.0)

4. restart Apache and if it complained about missing rewriteEngine.
Activate rewriteEngine with:

cd /etc/apache2/mods-enabled
ln -s ../mods-available/rewrite.load rewrite.load
/etc/init.d/apache2 restart

5. OX 6.18 should now work fine, now its time to update to 10.4 LTS with
apt-get install update-manager-core
do-release-upgrade --proposed

6. reboot as asked and run into a severe cyrus issue at boot.
Solve it with this guide: http://blog.mymediasystem.net/uncate...-doesnt-start/

make sure you backup cyrus as told in this guide, you will need that backup.

7. reboot your ubuntu and log into OX, if you run into a ajax 404 error, look here: http://www.open-xchange.com/forum/showthread.php?t=1729