Windows MCE and ABC 24 News audio via HDMI trouble

[fromaron]

I stumbled upon a very strange problem and don't know what to do now.
Here is the story:
My Acer X1200 HTPC (Win7 Home running MCE) with Ethernet TV double tuner (HDHomeRun) was working without any problems for years. All TV channels were working.
I was using DVI video output and analog audio output from the PC audio card.
Few days ago I bought new Samsung TV which has HDMI inputs and I obviously decided to connect my PC using the port.
With this configuration all TV channels work except ABC 24 News (my most frequently used channel). As soon as I tune to the ABC24 MCE gives me an error: Video Error, files needed to play the video are not installed blah-blah-blah.
All other channels SD and HD are working perfectly including other ABC channels.
So my initial thought was I have HDMI drivers problem as I never used HDMI with this PC before. Updated to the latest and no change. ABC24 refuses to play.
I also found on the net that it might be an audio problem, not the video one, even though it was reported as video error.
I disabled the NVIDIA HDMI audio driver and bingo, the ABC24 has moving pictures. Enabled the audio driver and the problem was back.

So it is quite obvious I have the HDMI audio driver compatibility issue with ABC24 News channel only
Hence my 2 questions:
1. What is so different with ABC24 News audio broadcast?
2. How do I fix the nuisance?