I agree with jrhoffman75, clearing the camera settings is the next best solution but if that does not resolve the issue then unfortunately it may be an indicator that there is a hardware issue with the CMOS sensor or the processor. Does this happen in both JPEG and RAW shooting?
Unfortunately if this happens in both JPEG and RAW shooting, and it shows on teh camera LCD as well as when you import your images to the computer, that would indicate a serious malfunction with the image sensor or processr which typically needs repair to resolve.
It is my understanding the there are no longer repair parts available for the EOS 1DS Mark II so Canon would not be able to service the item, but you may be able to replace the item at a discount through the Canon Upgrade Program. The sales department handles the Canon Upgrade Program and they can be reached Any day except Sunday 9am to 9pm EST at (800)385-2155.