Hello Stella,
If you have a drop in bobbin the chances are that when the bobbin case jumped out the little spring to the right got slightly bent, your model is not a UK model by the sound of it and there were slight variations but if this does not help then get back to me,
Take the bobbin out, take the bobbin case out, and make sure the flat spring clip on the right hand side is lifted just over the screw and moved to the right, make sure the needle is all the way in the up position, take the bobbin case and slide it onto the raceway making sure the raceway fits into the slot on the bobbin case and move the bobbin case to the left so it can go no further, you should then be able to just move the spring clip to the right to fit over the screw, make sure you put the bobbin in the correct way round, this would have been the probale cause for the cotton bunching up, it sounds like you have a drop in bobbin and not a self wind bobbin (touch and sew) if you have a seperate bobbin case that fits into the side of the machine let me know, hope this helps but get back if you want.
Ken
drivewithken@blueyonder.co.uk
Ken Dourof, May 2007