I have a Canon PIXMA iP4000 which, till now, has been first class. Today, I changed the cyan ink cartridge and learned shortly after, when it wouldn't print, that I'd not pushed it fully home. I did so and tried again. Now, the colour balance is wrong, apparently missing the cyan element. If I print a nozzle check pattern, the cyan's OK but other bits that would normally include cyan are the wrong colour (text and coloured blocks that should be grey/black). If I edit a colour photo to put extreme cyan balance on to it, it still prints out exactly the same as if I don't bother.

I checked the cartridge I replaced and spotted a possible cause. The type I usually use is the BCI-6C but I have mistakenly bought and used a BCI-6PC. It looks identical in all respects and when I put an old one back in, no change, still no cyan. I've gone through the clean/deep clean cycles to no avail. HELP!