Oh that nasty sewing Gremlin. You would think that he would take a day off every now and again. He stopped by here yesterday to shred some thread and skip some stitches. And just as quickly as he showed up....he left. I'd try rethreading both the upper and lower thread. Check your tension on top to make sure that nasty gremlin didn't move it. I've a different model brother that seems to be very picky. It doesnt like the least little bit of fuzz build up or loose threads in the bobbin area. So you might want to try cleaning and oiling if its allowed on your machine. Mine says not to but I find it works better if i do. I think they say that so we have to take in to be serviced more often. Good luck chasing out that nasty little booger, but dont send him over here!