Actually, had one happen to me today. Yesterday, had gone on a sew day with my guild. We sewed a couple of hours. Put machine into carry case and came home. During the night I woke up and thought I would finish project. Machine would not stitch. I could hear it humming and the wheel was spinning but the needle would not go up and down. Frustrated, I took it apart and cleaned out all the fuzz around bobbin. Put it back together. Nothing. I sat there staring at it for about a minute. Then realized when I had put it into carrying case I had slid the bobbin winding lever over and the clutch was not engaging. Moral: Stay in bed.