QTR-Quadtone RIP

Hello all, I'm new here, a photographer and not terribly computer literate so please bear with 
me. I just got a new Mac with a new system, Tiger I believe. I downloaded the latest version 
of Quad Tone v.2.6 March 08. Prior to this my prints looked great. Smooth tones great 
transitions between shades etc. With the new system I am suffering from what I believe is 
micro banding. My printer is an Epson 1280 with CIS. I scan at high res. print at 2880 use 
high quality paper etc. I would greatly appreciate any advice or help. Thanks, Paul.