Have you tried with a flattened copy of one image?
Are you images low key, high key color, black and white?
Could you post your printer settings (you can host your images on pixentral)
What blacks are you using?Photo or Matte? what profile do you use?
Look at this page for more info: <http://www.computer-darkroom.com/ps10_print/ps10_print_1.htm>