Digital BW, The Print

I am having a problem with the transitions of tones in the bottom end 
of the gray scale. Almost a slight posterized effect. I am using 1280, 
EEM, Photoshop CS, Adobe 98, 2.2 gamma, MIS ut2 ebi inks, P Roark's 
neutral curves, photo and matte setting, no colour adj, 1440, high 
speed off. I've also tried Elements and sliders instead curves and 
several other combinations and still getting the same effect. Has 
anyone else come across these problems? Any help would be greatly 
appreciated.

Thanks
Corin