HDMI audio device detected by the system but not listed in Sound Settings
It is certainly just a graphical matter because using hardinfo, running pacmd or trying to switch to HDMI in XBMC works, it's just not listed in System Settings -> Sound.
From the screenshot you can easily verify there is no HDMI output listed.
This is a regression from Oneiric, which correctly shows all the available hardware outputs on the same computer.
DistroRelease: Ubuntu 12.04
Uname: Linux 3.2.0-19-
Date: Wed Mar 21 15:59:43 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20120318)
UpgradeStatus: No upgrade log present (probably fresh install)