Silly question - did you rethread it properly? I would especially check the direction of the bobbin and that you've left enough of a tail on the bobbin thread for it to be picked up.
Next, look at the bobbin case itself and see if there are any burrs or little holes on the flat part that sits towards the back. If there are, you can often file them down to get things working again.
When you had the problem piecing, was it a "violent" sucking down of the material or something more gentle? Did you do any tugging on the needle trying to get the fabric out?