Cyan won't print

I have an identical problem with my MX700, and we're not alone (see http://www.nifty-stuff.com/forum/viewtopic.php?id=4414&p=1)

I have thoroughly cleaned the printheads, and verified that ink is flowing (blot the printhead onto a paper towel; you should see five colored stripes (one yellow, two magenta, two cyan) corresponding to the five rows of inkjets, each of which generates one of the colored stripes on the test page.

The problem seems to be electrical: the row of "light cyan" jets is not getting a signal. I'm going to try replacing the printhead; if I'm lucky, that's where the fault lies. If that fails, the problem is deep in the cicuitry, and my best bet might be to replace the printer. :-(