I have made 17 crazy quilt designs that came out great; #18 has broken 5 needles already. Could it be because I calibrated the screen before I started? Doesn't seem possible. I have a D1.

I also have the d1 (don't you just love it), either your thread is getting hung up so just use a spool holder or your bobbin is knotted. I've had this happen a couple of times. If these fail you may need to put her in the shop (YUK) good luck

Could your top thread be winding itself around the spool holder and causing this? Had this happen to me some time back and changed thread over to a stand,everything was back to normal again.

I don't really know the answer. Have you tried changing the bobbin. This brings you back to the top.