It might be your color format. In Photoshop, a nice deep black is a combination of CMYK or RGB, not just 100% black. 100% black will look gray. That's just the nature of the relationship between print and screen. While something may look nice and dark on screen, if the black is a mixture of CMYK and not just 100% black, there is a risk of misregistration when you print the file, and everything will come out blurry and offset.