I, too, went to install a new cartridge (blue) and now I have a fatal error on my my C7280 all-in-one. I called hp support and they offered to give me a "reset" code for $20 (because I am out of warranty). I have been through this before. About two years ago my printer conked out and they gave me a code which didn't work and then sold me an "upgrade." They offered to do the same thing this time, which sounds like a scam. So I didn't pay them anything but now I have a broken computer and no reset or obvious fix. If anyone has a suggestion for how to fix this thing other than to throw it out the window and buy a different brand, I would appreciate it. Thank you.