First you need to upgrade the nVidia drivers to the latest version - go to the wiki and on the page Display Drivers there are simple instructions on how to do this.
Next, hit the '1' key so that you get 'no signal', then grab a copy of your /var/log/Xorg.0.log file, read through this log as it will tell you what is happening when the graphics chipset selects that output.
Finally, be aware that many Samsung TVs can be a bit funny about which HDMI input you should use. Sometimes one is marked differently to indicate this.