Karen that has happened to me also..... certain kinds of threads won't work in some of my machines and of course I never remember to write down which ones they are! LOL One of my SK's will ONLY use cotton covered polyester! It is the fussiest machine I've ever owned! One of my other ones is not fussy at all and then I have one that I can't remember which brand it is but its the brand, not the type of thread, that it won't work with! Funny how that is!
But the good thing is as soon as it starts acting up, (any of them) I know what to check first!