Digital BW, The Print

Hi,
I just changed the inkset of one of my 1280's, from VM to Ultraone, 
CFS setup. I have a good nozzle check, and the heads are as aligned 
as I can make them (they seem aligned to me), yet my print quality 
is very poor, and I can clearly see horizontal lines, not clear 
sharp lines, but a sense of lines, in the direction the printhead 
travels.
Any ideas, advice?

Thanks
Kevin Logan