Can anyone please help with this weird problem?

Our 16 month old TS9120 had been working great.  Then the cyan ink cartridge ran dry and was ignored until it must have damaged the printhead. 

By the time I was asked to help, it was obvious the cyan cartridge was totally dry and the yellow was warning to be replaced.  I replaced both the cyan and yellow, went through a cleaning and the cyan wouldn't print at all on a nozzle check. The colors that came out were definitely odd looking without cyan, but the nozzle check sheet still listed all the color rows in the test.  It's just that they were not the right colors and the cyan section was totally blank but for the ID column on the left. 

After a couple of cleanings even the yellow section stopped printing except for in the left column that identified the colors.  Then I did a couple of deep cleanings with no luck.  After reading about what lack of ink does to a printhead, I figured the original printhead was toast, so I ordered a replacement from Canon.

The new printhead arrived from Canon and after installing it, no colors at all would print - only the PGBK black would print.  The left column that identifies the colors had only the one row at the top with the PGBK.  All the other rows were missing.

I switched back to the original printhead (that came with the printer and ran without the cyan ink) and it started the same pattern with the nozzle check sheet - no colors at all, just the black PGBK row at the top of the sheet.

Any ideas?  I thought maybe there was something in the firmware that had a glitch, so I even updated the firmware from 1.3 to 1.4 but that didn't make any difference either.

I've run out of ideas so here I am - can anybody think of something else?

Thanks