I have an ET-2750, which still has 70-80% of the color in the color cartridges. I had a paper jam today, and after clearing it, the black suddenly didn't work. I cleaned the heads and printed out a test page, and no black at all, but all the color bars were there just fine. So I restarted, and after the restart, only yellow and black work. After a couple of cleanings, nothing changed. All the color bars are there for yellow and black, and nothing at all for red or blue. Several restarts and a firmware update haven't helped Thoughts? Doesn't seem like it's a clogging problem, I went from all bars to zero bars with just a restart. Is there some kind of software reset?