with this printer's set up, don't we have four different dx5 capping stations all pulling on 16 distributed ink channels? the cap top on a dx5 can't do an isolated failure of a single color like a dx4. the supply side is fine, but the vacuum side can't create this effect. very odd. i say there is or was a bad batch of cyan ink that went out and clogged all the cyan channels on these printers or there was a bad batch of manifolds (a less likely scenario).
take one of the manifolds off one of your heads and blast it clean with reverse pressure, or put it in a ultrasonic cleaner. there's really no need to buy and new one. just clean the one you have and see if you get any improvement. there is a chance that all of the cyan jets are clogged to but the fact that it will print a bit then fail points to manifold failure. there is a very very fine screen filter inside of each manifold nipple. ...much finer than the one in the damper. you can temporarily get enough ink past the filter for it to print a bit but the demand for new ink will cause failure. one thing though, ... when testing for improvement, put the magenta dampers on the head. do just one head.
i remember there was a member of the jv3 yahoo board that practically rebuilt his entire printer to only find out that there was a bad batch of black ink that he got a hold of. the process of elimination is leaving very few options.