I'm using Blender 2.73a at the default startup with the cube.
Using Perspective or Ortho, the length and width of the Cube is clearly dependent on the current aspect ratio of the Element HDTV elefw231 screen that I'm using.
If I set the objects scale I can counter and the cube looks like a cube and not rectangular.
Of course then I have to remove it. This is on my ATI Radeon HD 4650 Graphics. My Laptop is not like this.