It has been a couple of weeks now since the firmware in OfficeJet, OfficeJet Pro, and OfficeJet Pro X inkjet printers and all-in-ones using the HP 934/935, HP 950/951, and HP 970/971 cartridges began giving end users error messages and would not allow printing when certain aftermarket cartridges were installed (see “HP Inkjet Printer Firmware
