Normally is the card.
What type, brand and model of card are you using ?
D7000 has 2 SD card slot.
formatting in cam shd help...
RGB Metering & Focusing.
then it may be a your card reader (if you're using one). I had many corrupted photos when transferring with reader, but none when i plug directly with my camera.
Could be file system issue, which affects the image data. You can format the card in PC using a suitable / compatible card reader. Disable the Quick Format option in order to have the entire media checked properly. Cameras usually only do a Quick Format, which skips the media checks.