It's sounds like the printhead is clogged at the at the inlet and/or nozzles that service the black tank (cartridge).
Assuming that colors are OK, you could try a black cleaning cartridge.
If you're in the US here is a vendor that has them for your printer:
http://www.printpal.com/partno/bci-24.html
Verify that I have the correct one queued up.
With that use a printer prime page so you can focus on the problem area of your printhead. In this case, black.
Make one up using Paint (or similar) or use this:
http://www.ink-refills-ink.com/InfoPages/1primepage.htm
Follow the instructions that come with the cleaning cartridge and avoid using Deep Clean ! This dumps a lot of ink and loads up the waste ink reservoir in your printer which is not good.
Post back and let us know how it goes.