I'm on a Mac with the 10.6.6 OS. With any OS newer I have a problem with thumbnail previews generated from DNG files that were converted from Fuiji S5 RAF files by the Adobe DNG converter. When I click on the file name for a preview, when I access the preview in "Get Info", and when I highlight a file name and press the spacebar for "Quick Look" all previews are pink, pixelated, and completely unreadable. The previews in Bridge are fine and the files themselves are not corrupt. So far, my only solution has been to revert to OS 10.6.6. This same problem exists in Lion as well as the higher versions of Snow Leopard.