Sat 02-Mar-13 03:20 PM | edited Sat 02-Mar-13 03:24 PM by nrothschild
In addition to the above, I would try a new USB cable. You have some electrical defect somewhere, and this is the easiest and cheapest to diagnose. Spare cables are always a good thing to have in the tool box.
Also try a different USB port (edit: on the computer) to isolate a problem with the USB port in your computer.
If that does not solve the problem, try a card reader. If that fixes the problem after swapping cables and USB ports, then the problem is likely the USB port in the camera. That is probably an expensive repair so a card reader would be the most economical solution.
If that does not fix the problem, and it happens with other cards, then it could be a weak pin in the camera's card holder. Or perhaps some other internal problem, and that would be the worst of all possible outcomes. Worst because it would require an expensive camera repair if the camera is out of warranty.
If it were me, I would get some software like BeyondCompare to bit verify all the images, between the card and the target copy on the computer. Or you could use something like Teracopy to copy and automatically bit verify the target file. I use both apps for a number of things but don;t currently have a need to bit verify my images. If I even once had your problem I would do that.
Those are Win apps. If you use a Mac then there are probably alternatives to do the same thing.
The only problem with bit verifying is that you can't do any file renaming or IPTC embedding during your ingest. Otherwise nothing will match. But unless you edit every image you may not know if you have a corrupt image before you erase or reformat the card. Unless, of course, your Lightroom workflow forces that (and it may).
If you use compressed raw, either lossy or lossless, then it only takes one flipped bit to destroy an image. I've tested that idea and know it to be true.
It is possible that shooting uncompressed raw will not result in a destroyed image if only one or a few bits are flipped. We've talked about that idea here but I haven't tested the idea, nor do I recall anyone else doing that. But in a pinch, if you cannot solve the problem, that might be worth a try. Otherwise you might try shooting Raw+JPG Large Fine just to make a backup copy of each image.