Most often these solarization problems come from mismatching inks or refilling in the wrong order. If you have spare carts, it might be worthwhile refilling from the original bottles and seeing if that alone solves the problem. A couple of the inkjetmall Easy Fill carts for the 1430 are a good to have on hand for tracking down these kinds of problems.
The Calibration mode on the mac is for printing the ink separation files that come with the QTR download. It is a special print mode that fires each channel separately. You use this for setting and measuring the ink limits when creating custom profiles. You can print the ink separation-6 file in calibration mode with QTR print tool or the free adobe color printer utility to bypass color management on the mac. If you have a spectrophotometer you can measure the patches to see which order they are loaded and see if you did mix them up or load them in the wrong order. it is an easy fix with the .qdif (.txt) file, but a little more involved when editing the .quad file.
I just got a 1430 and the EB-6 up and running earlier this week for smaller home use (using larger format printers and Cone inks at the studio). My first tests with the supplied profiles show banding and posterization when printing very smooth gradients. I should be able to post my results with good scans of actual prints later in the week.
Making a 6-ink profile is not exactly hard, but it is an exacting process. The ink channels ramp up pretty fast and they overlap with the other inks more times than the k3 profiles (obviously) so they need to be finely controlled or the errors and defects will be plainly evident in smooth areas.
I used to be pretty relaxed about making K3 profiles, but what I have learned in creating a good number of profiles for 4-6 dilution ink sets over the last year (with QTR) is that the cross-over points need to be very precise and have more overlap (but not too much) to avoid those kinds of problems. Additionally, the test charts and ink separation charts need to be dried for at least 12 hours to stabilize and get an accurate reading—I haven't tested how many minutes/hours under a hair dryer or space heater it takes, but matte black can go from a density of 1.6 to 1.64 over the course of 12 hours (depending on the paper). It might not seem like much of a big deal, but different shades dry down to different percentages which can throw off your overlap calculations if you measure them prematurely. Linearization is also best done with the 21x4 random test chart to account for any variances in the measurement data.
This might have been a little too involved for your question, but I hope it helps.
Richard Boutwell