One colour ink is out (well it's still about 15% full but not recognised by the printer) and now I can't print anything, not even
just in greyscale 
I'm unfortunatly starting to assume this is simply a programing trick by canon to ensure you always purchase ink, as there is no physical reason to stop the printing working with an empty cartridge.
But just in case....
Can some Pleeeeeeeeeeeeeeeeeeease help me make this printer function