Clean the machine very well and adjust your tensions, if needed. I had problems with that with mine and it was some combination of those 2 things that solved it. Be sure to look for any tiny pieces of thread caught in the bobbin area. I have a really bright little LED flashlight that I use that really helps.
I found that my 2200 Mini doesn't like some threads as well as others, but with some experimenting I can get it to sew well with most thread.