Hmm... this seams like a problem with the print head. Thats the thing that you put the cartridges into, and then the ink goes on from there. If you havn't used it for a while, usually a bit of ink dries up and clogs it up. To fix this, you have to get alchohol to dissolve it. It might be a bit complex, 'cause I think only a certain type of alchohol works, and another will damage it. My best suggestion is to buy a new print head for the printer. They shouldn't cost more than $20, and most likely a lot less.
You might wanna do a bit more research on the alchohol technique. It works almost every time with printers that print screwy. I dunno much about it though, 'cause I just replace my print head everytime it screws up. I'v replaced it about 3 times now, bleh -_- I should just get a new printer.. but tis not like I use it much anyway >_> I leach of my schools printers *has found a way not to be charged for printing*