Digital BW, The Print

The problem is vertical banding in dark gray areas. Here is a scan of
a dark gray patch:
http://www.joshwertheimer.com/gsr/linesingray.JPG
This happens when printing on Heavyweight Matte, Photo Paper, or any
other paper I've tried. I don't expect the printout to be dot free,
but I would think I should get a continuous gray tone. Nozzle checks
are perfect. Head alignment helped a little. I am using the latest
drivers, and I got the printer yesterday.

Thanks.
josh