Digital BW, The Print

Does anyone want to help me rescue my Christmas presents this year?

I'm fairly new to the world of digital printing, but have a few 
years' experience in a traditional darkroom. Thanks to the help of 
this group, I managed to get my Epson 1160 working nicely with Paul 
Roark's variable tone inkset from MIS. I've been using cartridges up 
to this point, but have been planning to give away many prints for 
Christmas presents and decided to move to the MIS continuous flow 
system, violating the all-important "if it ain't broke, don't fix it" 
principle.

Anyway, I've had nothing but problems: nozzle clogs (eventually 
fixed); air leaks in the CFS (eventually fixed with a new CFS) and 
now: very bad banding. Essentially, I'm getting a band equal to the 
width of the print heads. On each pass, I get a dark line every 3/8 
inch. Above the dark line, there is a noticable lighter gradient fade.

I've run nozzle checks, and everything seems fine. I've run the head 
alignment, and once again can't find a problem. I've switched papers 
from very thick to very thin, and it made no difference. I've 
windexed a piece of paper (twice) and fed it through. No dice.

Does anyone have an idea of how I might fix this problem? Or am I 
destined to head out to the mall for a last minute orgy of buying?

Thanks!
Matt Nolker