I've discovered a couple of things that cause problems for me...when I get to sewing too fast then stop abruptly the thread will somehow or other end up wound around the spindle the spool sits on and when I (Miz. Oblivious) start stitching again the top thread stretches too tight and breaks, causing the needle to come unthreaded. Or if I forget to be sure both top and bottom thread are under the presser foot to the back when I start a seam, everything balls up at the edge of where I'm trying to stitch and it won't move forward at all.