Hello erin.
The reason the teeth are only moving up and down is because the dial for the stitch length is set too low, you need to look inside the machine near the stitch length dial to see if anything has come loose, take the top of the machine off or the side and see if anything has broken away, if it is not something simple unfortunately you will have to take that machine in for repair, it is not something I could talk you through unfortunately.
drivewithken@blueyonder.co.uk
Ken
drivewithken@blueyonder.co.uk, November 2007