Wouldn't be uncommon to see some areas in the other side of the Cyan go, as you did switch the lines after all, but they should come back after a cleaning or two.
What we're pretty sure of at this point is this: It's not the data ribbon, nor the lines, nor the dampers. That leaves the head, the capping station, lines to the pump, and the pump itself.
Since you're getting a pretty good pattern from the rest of your test print, I'd doubt it's the pump, or the lines leading to it. Next step would be to inspect the capping station for damage around the area that seals to the print heads. If there's a cut in it, or it's worn away, it wouldn't seal properly, allowing air to dry the ink. Chances are though, you'd see some degradation to the other side of the Cyan head as well, were that the case.
At this point, I'd think there may be a short on the head. Inspect it carefully to make sure there wasn't any ink that made its way to the circuitry of the head. If there is, clean it with a swab of cleaning solution, and let it dry before plugging it back in and giving it another shot.
Oh, I just thought! Very likely that it's also a crack in the manifold, the little plastic spike that sits on top of the print head. This would create an air leak, not allowing the pump to do its job, and would be entirely localized to one size of the print head. Without using too much force, see if you can wiggle the spike on the manifold and observe with light to see if there are any small cracks in it anywhere. There shouldn't be much wiggle at all if it's completely intact.
