The Metamodes have to relate to the Modes in the screen section or else it will not work. Below is my Metamodes and Modes lines.
Option "MetaModes" "1400x1050, NULL; 1400x1050i, NULL; 1400x640, NULL; 1280x1024, NULL; 1280x1024i, NULL; 1280x960, NULL; 1152x864, NULL; 1024x768, NULL; 800x600, 800x600; 640x480, 640x480"
Modes "1400x1050" "1400x1050i" "1400x640" "1280x1024" "1280x1024i" "1024x768" "800x600" "640x480"
As you can see I used NULL to make sure TV out will not work at the resolutions that are not supported by the TV out hardware. However nVidia has put a limit in software that TV out can not output 1024x768 even though the hardware can do this.
If you want TV out in games make sure you specify the resolution that outputs TV out. Also make sure saturation is set at about half by using nvidia-settings in order to get color.
BTW, I used Clone for TwinViewOrientation.