Verify that your TV supports the PC video format you are outputting on HDMI by testing a direct cabled connection from the PC to the TV. This will also help prove whether any VGA/DVI/Display Port to HDMI adapter you may be using is working.
USE EXTENDPROJECTOR ONLY MODE:
In Windows Vista or Windows 7, hold the Windows Key and press P repeatedly to cycle through display modes (Disconnect Projector, Duplicate, Extend, and Projector Only). On a Mac, open System Preferences, select the display pane, then select the Arrangement tab, and toggle the Mirror Displays checkbox between mirrored and extended desktop modes. Duplicate tends to have the most problems as this sends the native laptop panel resolution to the TV, which either the TV or Wireless HD adapters may not support. Extend tends to be the best as this will send the preferred video format for your TV out the HDMI port and the preferred panel/monitor resolution to the local display. This dual resolution mode can reduce performance during gaming or playback of HD video in which case Projector Only mode may result in smoother video playback on some systems. Use the Display control panel (Windows) or the Arrangements tab (Mac) to try these modes.
CHECK VIDEO FORMAT:
Use the Windows Display Control panel (or equivalent on a Mac) to set the video resolution on your PCs HDMI output to one of the following formats that are supported by the Wireless HD adapters: 640 x 480 /60Hz (VGA), 800 x 600 / 60Hz (SVGA),1024 x 768 / 60 Hz (XGA), 1280 x1024/ 60 Hz (SXGA), or 1680 x 1050 / 60 Hz (WSXGA+).