Top tension may be too tight. When quilting on a frame, tension needs to be looser than with a domestic. Go down a whole turn of tension knob, and try again. Also, be sure foot ( if adjustable on your model) is low enough, and lastly , make sure quilt sandwich is not drum tight and takeup bar's not too high.

When quilting on a frame you don't want the fabric to be tight like a drumb

Note - this is an 8 year old Zombie thread that was bumped by a now-deleted spammer.

Love glide thread!! When it starts to break
I need to change my needle. Agree to not put hand quilting thread in quilting machine.

My Tin Lizzie loves Glide thread, too. Be certain your needle is in the correct position -- a bit off center works for me. Like PP, I skip one of the threading holes. Good luck! I know how frustrating this can be, but you've gotten some great information by our fabulous QB members, their personal methods and watching videos.