I have similar problem. I'm not exactly a rookie but i can't make it work a Nvidia FX5500 to an Samsung full hd HDMI.
Using a 10 meters Dvi-Hdmi cable, tv doesent show anything, but recognizes my connection saying is dvi connected.
Video card instead (vith vga and dvi outputs), doesent recognize Dvi conection - the second monitor saying nothing is connected to it.
I tried a trick: to set manually the dvi to display 1920/1080 resolution, switching the outputs from my video board using an dvi to vga adapter and to make the second display the first display. The display shows the resolution above but when i swich back, it goes off.