Make sure the HD STB is connected to the HDTV via either component or HDMI and look at what input you are plugged into, many HDTV have multiples of each.

ENGADGET: How to make sure you're watching Super Bowl XLII in HD HD

This series adopts a discrete component configuration that separates the display section from the tuner section, and these two sections can be connected with a cable or by using an optional wireless video transmitter unit that employs AMIMON's WHDI technology.

ENGADGET: Sharp's X-Series LCD HDTVs offered with WHDI wireless link