It has been found the Nikon D800E has difficulty connecting directly with a machine running Mac OS X 10.9 and USB 3.
The solution has been either to use a USB 3 wall powered hub, or a tethered USB cable such as the one here:
http://www.shop.tethertools.com/TetherPro-USB-30-SuperSpeed-Micro-B-Right-Angle- Cable-C.htm
The thread this resolution has been found in is here:
Note: of course USB media readers that support the D800E media would work if you are just trying to load the images and don't need any tethering
to the computer.
More info will be added to this tip as needed.