Greetings from Sacramento area in CA. The Grandquilter takes a different needle. Can't remember the code for it right now but I get mine at the dealer. They come in little paper packets - not the standard needle cases.
How tight do you have your tension? I run mine through 2 of the loops. GQ can be persnickety about thread. It apparently does not like them all.
Are you aware that there is a yahoo group for grandquilter? I'd suggest you sign up with them too and get some more specific ideas. The guys and gals in that group turn out beee-outiful quikts on their GQs. Good luck.