Report "I have an ip100 that's worked perfectly since I bought it 6 months ago. I've changed ink cartridges several times, but may have a problem with the Black cart I changed today. (error 5100 appears). I would like to recheck the cart, but the print head will not move to the centre when I open the door covering the print head and I therefore can't get access the Black cart to see if it's properly seated. All sliding surfaces are clean and fully lubed. Do I have to remove the top cover to get access to the print head? If so, directions please?"