i had this issue with my new tv as well. Im not sure what type of tv you have but if it is possible change the refresh rate on your tv to 60mhz, 99% of graphics cards dont even use the 120 anyways. Also, set your resolution lower. Your computer may be trying to force to the TVS resolution. Set a default resolution on your computer.

if all else fails.. are you under the correct HDMI input?

you can do a quick test as well, power down your pc plug in the hdmi then turn your pc on. Best case is that your screen is black but glowing and the input boxes or "not connected" boxes disappear.