m3freak - I can't speak for tux-box1's issue, though what you're seeing is the lack of support for the ion2 chipset for hdmi audio, specifically on 10.04. I've also been looking around the internet and it appears that in order to get this to function correctly you need to update both alsa drivers as well as the nvidia driver as well as manually modify the asound.conf file. My initial thought was that instead of updating alsa and nvidia for these specific boards (though possible and I've scripted some basic detection and installation based on board type here:
http://svn.linuxmce.org/trac.cgi/ticket/1153 ) instead to wait for 12.04 to come out since all the updates required will already be there.
I'm curious, I saw in another thread that you had been able to get HDMI audio working. Would you mind describing what you did and what pieces of media you've tested (i.e. myth, dvd, avi, mp3, etc)?