By now you may have the problem solved. My machine also buzzed and would not sew. I called my Bernina dealer who told me to try moving the lever that is used to fill a new bobbin. (Mine automatically stops when the bobbin is full.) It looked like it was ok but had, in fact, stuck half way between on and off. The minute I returned it to the off position, the buzzing stopped and the machine worked. Hope it works for you.