[stomachmonkey]

Different manufacturers use various methods to hose you.

Epson printers us a chip to "estimate" how much ink is used and will disable the cartridge if it "thinks" it's empty even though it's obviously not. You can get a chip reset device from fleabay for a couple of bucks.

HP, you need to check the box, the cartridges have an expiration date. A "brand new" fresh out of the box cartridge will print like it has clogged heads if it is out of date.