My thought, always, with any kind of problem like this, with any kind of machine, is to contact the dealer/company - especially if you have already tried all of the well know, likely fixes (changing your needle, rethreading, using a new bobbin, turning the machine off for 5 minutes, etc). I know that so many members of these boards have a wealth of experience with mal-functioning machines, but for my money, once non of the normal fixes work, it is well worth spending the money to have a certified tech look at the machines.