I replaced the light cyan cartridge a few weeks ago with no problems at all. I've followed the same steps with the LLK and it did not recognize the chip. I've tried taking the chip out and putting it in a few times and powering on/off, removing all other cartridges, etc to no avail whatsoever.
Two of my colleagues took a look at both cartridges and agreed that they looked identical in what I had done... so I'm not totally crazy
Does anyone have other tips I can try? I really want to get things printing ASAP as it's marketing materials that customers are now waiting for....