Re: 1920x1080i ModeLine = "No Valid Mode" for GeForce 6600GT and Pioneer PDP-4270HD
You've got the xorg.conf edit going. Cool. Maybe tonight's the night you get going.
These guys are right, it's a parameter to the option. Should read:
Option "ModeValidation" "NoVertRefreshCheck"
I also agree that the modeline seems wrong. Try the "1080" one, not the "540" one.