My machines like the European brands of threads, Aurifil, Metrosene, Mettler seem to work best in my Pfaffs. Coats and Clark only works for a short time, before my tension becomes messed up. It has something to do with the way the thread is made. If you are having problems try one of these brands. Cheap and on sale is not always the best option for quilting/sewing.
Do your self a favor and wind 5 to 10 bobbins at a time. I like to have gray colored thread in my bobbin. It is a good blender and goes with about everything. Unless you are doing an embroidery project, then I recommend using matching threads, as sometimes the bobbin pulls to the top. Then you have a tension issue, which is a whole other discussion. I like this variegated gray from Aurifil. The spools of this thread brand seem to cost more, but, in fact there is around 1500 yards on one spool, which really makes it more economical than your average thread spool.
I recommend getting a thread box of some sort to avoid the madness that is a drawer of bobbins.