[kjc]

From your machine's user manual: http://www.brother-usa.com/ModelDocu...000_EN_185.PDF

You have not threaded the upper
thread properly. Correct the upper threading. page 16

You have not used the right combination
of fabric, thread and needle.
Choose a thread and needle that are
appropriate for the type of fabric. page 20

The needle is bent or blunt. Replace the needle.

You have not inserted the needle page 21
properly. Insert the needle properly.

Dust has accumulated under the
needle plate or in the bobbin case.
Remove the needle plate cover and

clean the plate and the bobbin case.