Have you changed the brand of thread that you are using? I have a Janome that does not like Coats and Clarks thread at all. It will bind up so thight that nothing will make it move. Using canned air will sometimes just push the lint further into the machne. it is very time consuming, but take a small brush and a tweesers and start looking inside to see what is jammed into the back of the bobbin case area.
Try a new needle, different brand of thread in both the bobbin and top thread and see what happens. Good luck. :(
nannapat