I just bought a Viking Sapphire 830 to replace my old Viking. I was wondering if anyone experienced it being tempermental about certain brands/types of thread. I was tinkering around with mine and it doesn't seem to like the Signature varigated I have. I was going to use it to finish up a quilt I'm working on, but now I might need to come up with a new plan for that particular project. I never had this issue with my old Viking; it worked great no matter what thread I used.