"please use audio 3 input for dvi connection"

I just set up a new HTPC with Windows 7 SP1 64bit

This is my exact build:
http://forum.xbmc.org/showthread.php?tid=114890&pid=938718#pid938718

I have it plugged into a Sanyo Vizon HD TV via HDMI cable.


The HDMI audio and video work fine.

However, everytime I boot, a big blue box appears in the middle of the screen for about 20 seconds which reads "please use audio 3 input for dvi connection"

It is very annoying, and it never appeared when I was using my last HTPC (which was an Asus EeePC 1015pn, which I had to replace due to overheating issues)

Does anyone know why this may be happening?

I tried google but I could only find issue reports that involve a VGA/HDMI converter.

Many thanks in advance!