Have you installed the Nvidia drivers yet? If you have you may want to look at your /etc/X11/XF86Config(-4) files to see what changes need to be made for the TV out.
I have never used the TV out but I think you have to install the drivers before they will work at all for the TV out portion. After that, search
www.google.com/linux for you model and 'xf86config'. That will give you examples of what the file should look like. You can search here to, that may help.
Of course, someone that has that card may come along and post his/her XF86Config file too.
Hope that helps. google for linux is a god send. Try it. It works.