My printer just stopped printing yellow and black on most photos. It will print the yellow lines at the top of the nozzle test, but no yellow blocks below and it won't print yellow or black on the head alignment page. On that, I get only cyan and magenta alighment blocks. Anyone know what is happening? It has worked for a couple of years without problems. I have Canon inks except for the black, which is from Staples. I put in a new yellow, but that did not help. I don't see a good way to get the head off without really taking apart more than I would want to. I can get the top cover off and have figured out the buttons. Main light is green all the time.