This isn't a fault with the printer, IT IS A FAULT WITH THE WAY IT HAS BEEN SET UP!|
The problem is, not all of the tabs have been removed from the PHD unit inside. In order to remove these, you need to open the front cover of the printer, move the four tabs 90 degrees and pull the whole PHD out. You will then see the four yellow tags on the side.
Having printed with the tags in means the PHD has been potentally damaged. If you're lucky, you'll get away with removing the tags now and it will return to normal after about 50 pages, it not then you'll need a new PHD. The reason the problem manifests itself with black first is because the black is the most commonly used colour.
For info on removing all the tags, see here: