The INFO button is telling you what the incoming resolution and Hz is. If the panel is a 1080p/120Hz panel, and the incoming signal is 720p/60Hz, it should be understood that the television will upconvert that incoming signal (shown in the INFO bar) to 1080p/120Hz.
Does that help explain?
I have a PN50A550S. When I hit the info button it says that the signal is 1920x1080i. Shouldn't it show up as 1080p? The only piece currently connected to the tv is a Motorola DVR from Comcast via HDMI. What is the problem. Thanks