Thank you for your prompt reply. I now have gotten it cleared, but first, let me go back to your questions, as they are relevent (I think).
The LLK cart did not run out. It was at least 2/3rds full. Since installing it (about 10 days or so ago) I made a number of 8.5X11 prints, one 11X14 and 2 13X19 prints, so it was working fine. (when first installed, I had a few clogs - not a total shut down, but that was resolved with cleanings). Ink flowed fine through the cart when primed with no resistance that I noticed. (I did change over to another Inkjet Mall cart a few days ago - LM, but that shouldn't have affected the LLK)
Today, I decided to prime again and removed a larger amount of ink (10-15ml). I ran a nozzle check again, and still no LLK - none at all. This time, a few broken lines in the photo black showed up. Even though I ran cleanings yesterday, I tried another power cleaning today. Finally, things cleared out and I am now making a print.
What do you think happened? It sounds like air somehow got into the line, but as I had not changed the cart, and it had not run empty, what could have happened. I am wondering if the problem will crop up again. One day it was fine, and the next, a complete cut off of the LLK. Also, I make prints frequently (almost every day) so the printer almost never sits unused.
With all of the cleanings, I have just about filled the maintainence cart. I am almost out of yellow, but already have the Inkjet Mall replacement yellow, so will be changing over to that real soon.
Any suggestions are very much appreciated. What does this sound like to you? Could there be a problem with my printer unrelated to the cartridges?