I looked in the quick start guide as to how to open a picture, but after I follow instructions, they don't show up in my thumbnail strip. I have a folder of DNGs, and the select type to open includes DNGs. When I go to the folder, nothing happens, no thumbs. When I go to a folder of TIFs, it shows them fine. So, how do I open a DNG with this program? What the heck am I missing?