The jam problem doesn't go away if you unplug the printer. If you say that the Jam didn't happen then the software which handles the printer had errors and reported a jam out of nowhere. Unplugging it will simply retain the error in printer's memory and the next time you open it up the error persists. Instead try and hold the power button for a couple of seconds and you will see that the printer will reset it's current settings and any errors that are stuck in its memory. If the problem persists, you should perform a new installation of its software and use the maintenance tools available including error clearing and default settings.