I have the same problem with HP OfficeJet 5255. Have tried the reset method numerous times (including removing ink cartridges) and nothing helps. Keep getting the "watchdog" error message. Cannot connect to computer by USB or by wireless, therefore I am unable to update the firmware. Also cannot access settings or other options on printer control panel. What else can be done to reset or to update firmware if printer is not recognized by computer?
Thanks,
Ken-Bonterra