I had something similar happen with my D300 and I posted a question on that forum a few months ago. I got responses ranging from a bad shutter, to a bad card. My issue eventually turned out to be a bad connection between my card reader and my computer. I bought a new one and the problem ended. An easy way to test for this is to re-upload the pictures and see if either the problem goes away or you see the problem but other images are involved.