Sounds like Tak had the right idea. You probably need to calibrate, or make sure the calibrated settings are being used.
The first one would be accomplished using something like Colorsync or Adobe Gamma.
The second would be things like making sure settings are correct in your program (the right profiles are used) and making sure you're using a good profile. I generally suggest adobeRGB1998 for working with photos as a nice wide rgb profile. Then make sure you are passing the data correctly to the printer by
not changing from RGB format unless the printer requests it specifically and by
not letting the printer do any color management, just send the files
with their profiles directly to the printer. This is usually set in the print dialogue box.
I would do some searches on "calibration" on the forum or on google and then if you are still stuck after reading the plethora of information available, come back with some specific questions.
Good luck.