Assuming your measurement of distances and shooting methodology is correct, one must conclude that either (1) the aperture is not actually f/4, (2) the focal length is not truly 24mm, or (3) the circle of confusion is not 0.03mm.


The precise hyperfocal distance with those three parameters is 4.824m or about 15 feet 10 inches.


Here's what I think is probably happening. The 21MP sensor of the 5DmkII has a resolving ability that exceeds the traditional 35mm film and therefore when viewed at 100% crop you are no longer dealing with a CoC = 0.03mm. In fact, I believe that if you are going to use the hyperfocal technique to achieve sharp focus at infinity at 100% crop, you will need to use a much smaller CoC, resulting in a longer hyperfocal distance.


I would explain this in more detail but I think the Wikipedia article is a better reference: http://en.wikipedia.org/wiki/Circle_of_confusion