HDMI Audio out on MSI Meda Live

[GyroTech]

Hi all
I'm running Mythbuntu on an MSI Media Live PC and am trying to get audio 
out working via the HDMI connector. I have been to the mythtv wiki and 
followed instructions there 
(http://www.mythtv.org/wiki/index.php/MSI_Media_Live) being install 
version 1.61 of the BIOS and disable 8ch output there, as well as 
setting mythtv to ALSA:spdif output.
When I connect a set of normal speakers up to the front panel output I 
get sound just fine so I know that much is working. I don't have another 
other HDMI devices to test with so I can't know if it's the cable but 
I've been told that any HDMI cable will carry audio as long as the 
source outputs the audio.

So if anyone has any pointers on where to start for me to diagnose and 
solve this, let me know...

Thanks,

GT