I'm not sure where to post this, but here's my problem:
When I copy dng files from the computer's internal harddrive to an external hdd, many of the files become corrupted (my guess). When I open the copies, photoshop just tells me that it "Could not complete your request because Photoshop does not recognize this type of file." On OSX one can usually see a preview thumbnail for each file, but on the corrupted files there is only the dng symbol, and when I enlarge it for preview it also won't show the image.
The original files all work perfectly fine. Weirdly, not all copied files get corrupted. I tried two different hard drives, both had the same problem. copying to a different location on the internal hdd works without problems.
Has anyone encountered this kind of problem? I couldn't find anything like that online, I don't even know if its a hardware or software related issue.