Digital BW, The Print

I've started to have more pronounced horizontal (parallel to the 8.5"
side of 8.5x11 paper) banding and I'm trying to figure out what is
causing it and how to fix it.  The problem seems to be becoming more
pronounced as I print more.  The banding is across all tones although
it's more visible in certain tones.  

This morning I ran the head cleaning and nozzle alignment which
resulted in no visible change.  The only way I was able to improve it
was using one of the glossy paper types and turning on super
microweave, however that didn't work well on matte paper.  

Is it possible that one ink running low could cause it?  I think at
least one ink has been less than 20% for almost all the prints I've
made recently...

Any other ideas?  

Thanks,

Brian
http://www.brianchapmanphotography.com