I have both an Epson R1900 and an Epson P-600 and it is always the yellow cartridges on both printers that have problems. I wonder if the pigment in the yellow cartridges has a higher tendency to gum up either the print head or the cartridge. Many times when the yellow cartridge stops working, swapping it for a brand new one works instantly, no cleaning required. This makes me think it is definitely not a printer problem, but a cartridge problem, specifically for yellow pigments/inks.