Well, that would fall under the category of "foreign matter" in the bobbin area then would it?! LOL I just knew it would be something simple! It usually is! LOL Glad you figured out the problem and can get back to your sewing now!
We are in the process of cleaning and oiling some of the older machines we have here to see if we can get anything running ... its kind of a fun project! DH is doing all the cleaning and oiling and then brings them to me to sew and adjust, sew and adjust! LOL