I have a canon mp780. Shows an error code of wrong cartridge, even though I have replaced all the cartridges with new canon ones.

it may have messed the cartridge holder. call canon for help for replacing the piece

replace you cartridge with (BCI-3eB, 6BK, 6C, 6M, 6Y)

I had the same problem on my pixma mp780. I cleaned the printer head. it worked for about a year, but then i had to replace the printer head. after you clean or replace it reboot it.

You get that message when the printhead goes bad. It's not the ink cartridges. You need a new printhead
# QY6-0049-000 around $60.00

On this machine it means the printhead is bad. QY6-0049-000 around $40.00

Try to reset to factory .
Remove ink cartridges and print head.
Power off machine and unplug for 10-15 minutes.
Restart machine and install head and cartridges.

It is probably one of the cartridges. Usually, when the message "wrong cartridge" appears, the cartridge is faulty.

Overnight I started getting the "wrong cartridge" message on my Canon MP780. I use only OEM cartridges. As the Canon website suggested, I replaced the printhead with a new one (Empire Office Machines for $48.25 plus shipping) and it works great. Prints better than ever. Easy fix for my machine. I did read that using refills can cause more problems than just the printhead.

the only solution that will work is replacing the print head. I checked with canon and that's what "wrong cartridge " means. I have had this with one of my own and one from a client and both are now fine with new printheads.

Go here and type in ERROR LCD: WRONG CARTRIDGE

Follow steps carefully

http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=SupportDetailTabAct&fcategoryid=238&modelid=10444