THREAD FREYING

Don't yell, you're giving me a headache.

Check for burrs somewhere in the thread path, especially around the hook, bobbin case, and needle plate. If the thread on one needle is fraying, and not on the others, change the needle. Sometimes the eye of the needle will have a burr/sharp edge that will fray threads. Dark threads are more prone to fraying than lighter ones.

gwh

Sounds to me like you have a burr on your bobbin case or somewhere in the thread path. If you have a burr somewhere, you can use crocus cloth to "polish" it. Hope this helps...