What is error code C000 on my MX870 printer mean? How can I fix it?

[JohnTS]

I tried turning the printer off/on and shutting the cartridge door several times with no success.  What eventually worked for me was :

Removing the cartridges and cleaning the electrical contacts and the ink inlets; uninstalling the canon printer software; and reinstalling... Not sure which solution worked, but the printer is ok now, if only temporarily.

[Billfish62]

I accept the solution from Patrick, the Canon Expert, and will inquire into the Canon Upgrade Program.  

Also, my printer is an MX860, not 870; I mistyped.

In addition, my wife fiwed it by sticking a thin spatula into the printer casing and pressing on the tops of the cartridges.  This caused the problem cartridge to seat itself and the error went away.

BTW, I have never had a problem with this printer in its long lifetime.  Go Canon!