Yes.
My print head was dead, and after trying all the advice on here and elsewhere, I never managed to recover it.
The price of a new printhead was almost as much as a new printer, so I reluctantly ditched the i850 and bought a Pixma i4200. This produces prints about the same as the I850, but...
Shortly after the above post, After attempting to clean the head following instructions found on this board and others, the print head gave up completely, printing only smears.
I have exactly this problem on both Magenta and Cyan nozzles.
I too have tried multiple deep cleaning cycles, water flowing, and also, (Nothing to lose at this point), soaking in electrical cleaning fluid. (By the smell, containing Trichloroethylene).
I can add some further datum points.
1)...