I have the same problem with my GeForce 6600GT.
the problem is due to the drivers, because when I uninstall the geforce driver.
the output works fine with colors.
if I can use an older driver, then it probably will work.
but unfortunately, GeForce 6600GT does not support older drivers.
I've searched all over the internet for a solution, but all the people who reply talk about the TV format, the connection cables ... but those are not what caused the problems.
so, I guess we can only hope Nvidia will release a new driver that will work.
or does anyone have a solution to this? maybe an unofficial driver for 6600GT that will work?