Hello Debs,
Chances are there is thread stuck in the raceway, force the balance wheel backwards as hard as you can and you will probably free it off, it only takes a very small piece of thread to jam the machine, if that does not work then it is stuck elsewhere and it will mean a process of ellimination, e-mail me if you have a problem.
Ken
drivewithken@blueyonder.co.uk, July 2008