Digital BW, The Print

I am doing a lot of black ink only printing with my epson 2200 (untill
I can afford pizo) sometimes I get some banding parallel to the motion
of the print head(I dont know if this is considerd vert or hor) I have
run through the print head align. a few times and still get it. I dont
seem to have any problems when doing color printing but I find myself
wanting to do mostly B&W lately so this is very fustrating. Do any of
you know what is causing this? thanks, Ian.