Same thing happened to me! I was sewing along merrily and suddenly all my tension was gone, rethreaded the top, turned her off, started her up, tension still made. I was about ready to return her!! LOL Went to pull the bobbin thread out to see if there was dust or something, and sure enough the thread had come off the little catch down there. Funny how much of difference that makes!! Fixed the thread and got back to merrily sewing along. LOL
Rachel