Datacolor User to User Support Group.

I've owned the Printfix Pro Suite (currently updated to Spyder3print v3.5) for several years and created a number of profiles with it for my Epson 2200 and 2400 and all of the profiles have showed strange uneven areas when you view a soft proof of the Granger Rainbow. Epson profiles on the other hand look very smooth.
I just bought an Epson 3800 and decided to give it a go and profile an Innova paper smooth cotton natural white. The profile I got looked like every other profile I've done on the Granger Rainbow:

http://www.ullinish.com/images/GrangerRainbow.jpg

with the strange inconsistences in the cyan area. In practice the profile works very well with out of camera images but if you push the saturation of blue skies it creates weird posterization effects.

Does anyone know why I am getting these artifacts? I have measured most carefully over many many attempts although I have never attempted to average measurement sets.