Xerox will not assume any responcibility if you are using generic ink, regardless of warranty status. I have seen it many, many times. I'd suggest figuring out who makes your generic ink. The name that comes to mind, is Media Sciences. They make a lot of the ink packaged under different names.
They offer a warranty on their ink, and will gladly replace your printhead and pay for the tech to come out and do the task. However, you are at the mercy of Media Sciences to send the printhead. I've had customers who got the printhead in a matter of days, and some that have waited 3 weeks for a printhead.
Timothy N. Couch
A1 Printech
Anchorage, AK