Which paper/media type did you select when you loaded the paper? It sounds like the media type either delivered too much ink, or it used the wrong black ink (MK vs PK) for that particular paper. There are several "special" media types for "glossy" paper (PK), Special 1-5, and for "matte" paper (MK), Special 6-10. Settings 5 and 10 delivery the most ink for those media types. I haven't used that particular paper, but my experience with the iPF6400 is that the ink is dry pretty much upon exiting the printer.
-Scott