We have our intranet built on joomla and we have installed the MaQma Helpdesk component and it works really well. It has ticketing, FAQ and Knowledge base. The paid for version has a client application and a troubleshooter.
When you created your image did you leave it off the domain and did you have Windows XP Support Tools installed?
Have you use the FOGCrypt utility to create a encrypted password that FOG uses to join the domain?
Check that apache2 is installed. If not sudo apt-get install apache2
If it is check that it running /etc/init.d/ apache2 start.
I must admit i havent tried it on ubuntu desktop 9.04, just 8.10 server and desktop.
You will need to enter the command sudo ./installfog.sh
It will ask you to enter a password, just enter the same password of the user you are currently using again.
put the command sudo at the start of the command you have just entered. It wil then ask you for a password just put the same password you are using in again.
It is recommended that you change the passkey for security. Have a look at the section Securing Active Directory Intergration on the wiki. Dont worry mate I had this bother when I first used FOG.