This does not look like a shutter or sensor fault. A horizontal offset/streak like that usually means the image data was corrupted after the sensor was read.

Most likely causes, in order, are:

• CF card corruption
• corruption during transfer to the computer
• corruption on the computer itself, such as bad RAM
• less likely, a camera processing/write issue

What to try:

1. Shoot on a different CF card.
2. Transfer with a different card reader/cable, preferably avoiding cheap readers, USB hubs, and questionable front-panel USB ports.
3. Test the files straight from the card and compare after transfer.
4. Check your computer memory with a tool like Memtest86.
5. Reset the camera to factory settings and update firmware if appropriate, but don’t risk doing that using a suspect card.

Since the same artifact appeared on two different D700 bodies, the CF card or the transfer/computer chain is more likely than both cameras having the same hardware defect.