I have a HP Deskjet 420 printer and whenever i try to print the cartridge moves into the middle and the replace cartridge moves to the middle. The replace toner light flashes and all stops. I changed the cartridge twice but the problem still persists, has anyone got any knowledge of this or am I being stupid? The toner is definately fitted correct and is the right one. I have XP Home, 256ddr, 40gb HDD.