Below is an image that shows the problem. The top part of the
image is an original image (both the photo and the square multi-color
thingy. Below that is how the image printed (I printed it, then
scanned it).
If it matters, this was printed on hp premium photo paper.
Anyway, it looks like the photo cartridge is vertically misaligned with
the three-color cartridge by .5mm or so.
Click on the image below to see the full-size image.