Thumbnails of large picture images

Hi,

I am having troubles with the thumbnail files of my Nikon Camera!

It is a D800 and all is smooth excepts for the finder thumbnails.

As you can see from the image I have selected the box "show icon preview" but only for D800 files it doesn't work.

My MacBoo pro Retina is completely updated and I have Aperture too...

I love the chance to select my pictures from the finder too...

Mac os is great for the workflow... but simply it doesn't work this time...

I hope that someone can help me.

Thank you very much