This is exactly what happened to me. Replaced Magenta and then started getting printhead errors and I can do nothing with this printer. I am only 3.5 months out of warranty. Are you serious, the answer is to buy a new printer????? I just replaced the last ink cartridge that came with my new 8600 printer and now your answer is to go out and buy a new 8600 printer. I bought an HP because I thought you guys had a good reputation. No way an 8600 printhead should fail with light use (lets see how many pages can be printed with the supplied ink cartridges when purchased new - not many) 3 months after warranty. Why would a printhead that was working perfectly fine before I replaced the last ink cartridge that was supplied at purchase. Something seems hinkey about this.