Hi Molly, I have Expression 2.0 and I also had trouble with my threader. Found out if you use a magnifying glass you can see the problem and be able to fix it. I couldn't see it but my husband could...he just had to bend a little wire that goes in the needle hole to fix. Also by the sound of your nesting on the backside, could you have possibly put the bobbin in going the wrong way ? This is all I know, but wanted to share it with you. Good Luck, I love my Pfaffs !