Re: Fleece sewers...question.
Did rethreading the bobbin work?
Did you try a universal or ballpoint needle?
Is this the kind of machine that has a separate bobbing tension (usually the kind where the whole bobbin case comes out and you put the bobbin in it and snap it into machine)? There is a screw on the bobbin case to adjust but I don't know how.
Usually for me tangles underneath indicate that something isn't threaded correctly. Rethreading the whole machine fixes it for me.