Thanks for your posts, gentlemen. I know it's been a while, but I'm hoping you're still following this thread and that your experience can help me out.
I haven't been as good as you guys about leaving the printer on all the time. I've had my Z3100 for about 3 years now, and I print 0-3 times a month. About a year ago, my PSU started making a HORRIBLE noise. As it was out of warranty and working fine, I tried to ignore it. But my maid turned it off because of the noise, and I left it off for a long time, maybe 2-3 months. When I turned it on, almost ALL the nozzles were clogged. I cleaned them with RO (reverse osmosis, nearly deionized) water and Q-tips multiple times, used the cleaning cycle dozens of times, and nearly emptied my cartridges half way, and I got everything working except, you guessed it, M-K. I finally broke down and got a new print head, and everything was good for a while... but after a few prints, I began to notice a weird phenomenon. The more I printed, the more nozzles I would lose on the M-K, and now, on the Blue (looks purple) also. I rest it a while, and everything comes back, but I print a little (even if I don't use the color), it starts losing nozzles! For example, I just printed a batch of grayscale images and the M-K lost nozzles, but so did B.
I think my supply lines are clogged. Anyone have any suggestions? Thank you very much in advance.
Incidentally, I ordered a new PSU for about $200, a lot less than they probably ran a couple of years ago. I thought THAT was all I needed to get a fully functional printer, but looks like I may need another major overhaul.