I am so sorry you're having this problem. There is nothing more frustrating than to sit down at your machine and, while it had been working fine just a few hours before, now it's really misbehaving! I had something happen (not exactly the same thing, of course), but I started to sew appliques on a whole-cloth top, and my machine wouldn't do anything! After looking around a little, I discovered that the tension spring on the bobbin -- well the screws had come out and the tension spring was lying just beneath the bobbin case. Believe it or not, as tiny as those screws are, we found both of them and now my machine hums along perfectly (that's really nice for an old lady -1963). Hope you can get it resolved. Best wishes.
Jeanette Frantz