If I'm in Photoshop at like 200-300% and I were to take a screenshot then I would get lines like that.
You might have an issue as well then. I just tried this. I loaded up one of my 7D shots and zoomed all the way to 500% and there are no lines. After 500% the screen switches modes and displays the pixel boxes, but no lines in the image.
OP, sounds like your plan is a good one. It is not normal.