Hello Sam,
To begin with a Bernina foot control is a lot of money, if the machine was running slow then stopped it is unlikely to be the foot control, when you put your foot on the control are you getting any buzzing sound coming from the motor ? if you are then undo the stop motion and push hard on the control, if the balance wheel whizzes round fast then the machine has stuck, if there is hardly any movement at all then chances are it will be a new motor unless the dealer can fit new motor brushes, if the balance wheel does whiz round I would suggest WD40 on every moving part of the machine that you can get to preferably leaving it overnight then try.
ken
January 2011