Thank you for all of these responses. I now think that 100 wt thread is just too fine to use on the top of my machine. When I bought it, I wasn't thinking about the weight, just the great colour and good brand name. I tried using it for hand appliquing a butterfly and it was perfect (thanks for the suggestion Peckish). My next thing will be to only use it in the bobbin. I now know quite a bit more about thread and appreciate all of your thoughts.