Are you using the same thread on top and in the bobbin? What size thread is it? Is the needle too small or too large for that thread? Is your quilt level with the bed of the machine and less than a pinky finger's distance above it? What speed setting is your machine on (high, medium, low)? Is it the top thread or bottom thread, which is breaking? If it is the top thread, how many holes are you threading the machine through in the pretensioner? Is it a normal spool type or cone type thread? Are you using the telescoping vertical thread guide?