I'm having the same problem, pseudoquilter. I sew about 2 feet on a straight seam, then hear the "clunk" and see a lot of threads in the bobbin area. I cleaned all the gunk around the bobbin area and rewound another bobbin. What I have done since has been working. Hopefully, it keeps on working or I think I will be looking for a new machine. Mine is pretty old. Maybe it's just a Michigan problem. LOL