Printer doesn't use the black ink for printig black
Binary package hint: cups
By default (Printout mode set to "High Quality (Color Cartridge)" and Resolution, Quality, etc set to "Controlled by 'Printout mode'") the Printer doesn't use the black ink for printing black. It assembles all colors to something like gray.
If you manually set Resolution, Quality, etc to "600dpi, Color, Black + Color Cart." all works correct.
So the correct behavior should be: Resolution, Quality, etc set to "Controlled by 'Printout mode'" uses also the black cartridge.
PS: I have a HP Deskjet D1560 connected to my router and used as a network printer (setup as AppSocket/HP Jet Direct).
My System is Ubuntu 8.10, CUPS 1.3.9-2ubuntu7