I have the same problem, even when using the Print plugin..
My prints are very dark and sometimes oversaturated.
At times it seems to use the matte black even on glossy prints.
I have only printed glossy prints and still I have used a lot of matte black.
I notice that the matte black I can rubb off the paper with my finger..
No idea what could be wrong ..
I will check with my dealer tomorrow and post an update if I get any useable info..
When printing through Photoshop CS 2 v 9.0.2 on a Mac G5 v 10.4.8 to a HP Photosmart Pro B9180 pigment ink printer and using Print with Preview/Color Handling/Let Photoshop Determine Colors I get prints that are very dark and sooty looking, but if I use Let Printer Determine Colors the results are very good and quite accurate.