Digital BW, The Print

After a rather frustrating couple of days, I am still having problems printing images with 
100% black backgrounds.  I am using the 1440 super dpi setting, ordered dither and matt 
paper.

I am getting, every inch measured from the right side of the image, a 2mm or so thick 
_line_ where the ink laydown is _interupted_  I can see this effect occurring as the ink is 
laid down on the paper. So every inch there is a vertical line across the background.  (It is 
not a roller problem.)

As a test I created a new image in PS which was simply a black square of the 100% 
background colour.  The effect occurs when printing this image also. On the test image, 
adding 1% noise helped the problem, but this worked on one but not on another real 
photo.

Printing at 1440dpi (rather than 1440 super) tends to create very fine horizontal banding 
and a very unacceptable result.  I have a good nozzle check and the MIS purge pattern 
prints well. 2880dpi does not work with matt paper.

What gives?  Does anyone else see this happening? Can someone else try my black square 
test?  If it is my printer, what could be wrong with it?

Thanks


Steve