"wrong cartridge"- Printer is giving us a "wrong
I am having the same problem with my MP780 mine started doing the same thingafter deciding to use Calidad inks the large black ink leaked into the yellowink (stick to canon inks).
What I have done so far with no success -
Replaced the ink cartridges with new ones supplied by Calidad, still the sameproblem.
Removed and cleaned the print heads manually and to my surprize after soakingin warm water and multiple cleanings for over 1hr black ink is still coming outof the yellow ink head.
I still get the same message after all I have tried...
One thing I did manage to do is prime the yellow ink and got it flowing throughthe head again but it's still mixed with black... I wonder if you may have runout of magenta and dried the head...
Try priming the magenta ink by removing the head (don't touch or wet the metalcontacts at the rear, the ink heads are on the bottom) place on a clean lintfree cloth (or I just used damp tissues then dry tissues) you should get onelong black strip and two cyan, two magenta and two yellow strips on the tissue,if you do not then try priming by replacing the magenta cartridge and gentlypumping the cartridge up and down repeat until you get the ink flowing.
Replace the head and cartridges, press ok, turn the printer off then reset.
Let me know if it works or if you come up with another solution that works as Iam still trying to figure out how to fix mine.