My HP Officejet 4650 recently started to become non-reactive on a frequent basis. Sometimes the display just glows but the touch screen doesn't work anymore, sometimes I get the error message 0XB97BC510 (not sure if 0 is the letter or a zero). The power button also becomes non-reactive, so only unplugging the printer will solve the problem but only temporarily.
According to the HP software ("HP Druckerassistent") the firmware is up to date. The printer is connected by USB-cable to my desktop PC and also being used as WiFi printer. Until recently that combination worked just fine.