That is a tell-tale sign of a back that is out of calibration tolerance for the new Flexcolor software. I had the identical problem, and I re-installed, re calibrated and re-did everything for the back. Nothing I could do solved the problem.
Here is the deal, as I understood it from Hasselblad, in Redmond.
Flexcolor 4.6 has a new de-mosaic algorhythm (sp?) that gives great new detail, but also shows up the tolerace issues with the older backs.
Such as my V96C. If the file has already been imported via 4.6, there is nothing you can do. If you still have the files on your image bank, you can re-process the file in 4.3 or 4.2 or an earlier version, the pattern will not be there, but you'll notice some very small artifacts around fine details at about 300 or 400%.
And this is not pixel-peeping, because it's a variable thing - sometimes it's clear as a bell at 100%.
And it sucks.
The solution (well, my solution) was to send the back to Denmark and have it re-calibrated. I've not shot too many blue skies with it recently, but it appears to work perfectly now.
If you have any other questions, feel free to contact me at email@example.com