Thank you for the suggestions. I did try rethreading the machine but not a new bobbin. I have the same thread top and bobbin. I use coats and clark cotton. Maybe I should try one of the other brands. I'm confused because I had no trouble piecing with the same thread. Oh well. I'll try a new bobbin, a larger needle (I have some 18s) and I'll get back to you.
Again, thank you all for your suggestions. If worse comes to worse I'll quilt around the batiks. Seeing as the top is made of 1" and 2" squares and rectangles this should be fun!
bev.