H1D22mp is good at low iso. iso400 is grainy.
Check the Lowpass filter on the back carefully. In some countries it has fungus problem on this filter.
You need to send it back to factory for filter replacement.
I have had that problem on the 132c -- it was a short trip to Denmark , it wasn't fungus but an early manufacturing problem from some sort of sealant used and I think only affected the early units like mine and not the later ones. Its pristine now and should stay that way.
I bought the H3d 39 from the Pro centre - all cleaned up by Hasselblad and good as new with six month warranty. A very good deal and a safe way to buy only 5000 odd clicks on the camera. 400asa is not that grainy anymore! Newer firmware and software have really sorted it, I only use it in real emergencies but have been pleasantly surprised. he big pixels at that size capture plenty of light so its always had room for improvement.
I have only used the H3d at 200asa so far, but could only tell later by the exif data, grain is there but only just and not anything you would ever see in print.