Assuming you aren't using a PC-input but rather a normal HDMI input to the HDTV you should be using the HDTV setup in the Video Control Panel not a regular setup.
If it's a typical HDTV you'd likely use 1080p_60 NTSC for the setup, then fix any SCALING issues.
You can also have issue if you are trying to CLONE screens and the 1st screen is a lower resolution.
Finally, if you hear no audio then change the Playback Device to the proper HDMI output such as NVIDIA_HDMI).