GUI position not updated on build & run

I'm using the RotatableGuiItem script which is lurking around this forum. It works fine when running in the Unity editor, though when I build and run the project the position of the object is no longer updated. An example of my problem can be found here (includes all required files to run).

Use W, A, S, D to move the box. The indicator is around the middle of the screen and will rotate and move to point towards the box. When I build and run the project the indicator will rotate, though its position will remain in the top left hand corner of the screen. I am not sure why.