Welcome to Nikonians! Guide mode is reset to Easy operation> Auto when the mode dial is rotated to another setting or the camera is turned off. If no other option is selected when the shutter release button is pressed, the camera will take the picture in Auto mode. See pages 35-40 in the D3000 Users manual. If that doesn't work you could try Resetting the shooting options. See page 119 of the D3000 Users Manual. Good Luck and Enjoy your Nikons!