I doubt it's the timing, but it's easy to check. Take the bobbin case out of the bobbin race. Now take off the faceplate and look at the bar connected to the needle bar. There is a little ring around it. When that ring starts to disappear into the little tube, the needle should be just about to meet the hook inside the bobbin area. Thats when you know it is timed correctly.
I agree with Joe, there is probably a stray thread still. If you don't see anything when looking in the bobbin area or rough the feed dogs, try looking up through the bottom of the machine.