Thanks Meq123 for the workaround.....
Same story here - new Gigabyte 8600GT card, Sony KDL-40X3100 - HDMI cable and Gigabyte P35C-DSR3 Motherboard, and my VISTA install.
Managed to find the Phoenix Edid application here:
http://www.softsea.com/review/Phoeni...-Designer.html
I used the latest Nvidia drivers (175.19) PQ is excellent.
Quite perplexing until my wife said: "why don't you ask some of your nerd friends on the internet" and sure enough I wasn't alone!
Now I have a nice new gold plated 3.5mm to RCA cable for my troubles (I thought the old one was broken!)