When I got my Janome 6600, that happened to me. And with that machine,, you can't just open the little door and see that the thread jumped out. So I spent too long unscrewing the throat plate and clearing the thread out and the fabric was getting all jammed in the hole. I didn't use the auto cutter either which would have saved taking the plate off numerous times. Finally it dawned on this brain of mine what was happening and I was able to fix it and continue with my project.