Joe--you are spot-on about the threading (in your first message here). This is what the lady at the shop taught us. Now, I will correct what you say about the manual--it is very hard to tell that you need to make use of the "hook"-like part of one of the disks *and* thread through that little looped gizmo near it from the manual.
Just standing my ground here
Thanks for the advice to both of you about the foot. Joe, I am going to contact you directly if that is okay in the future, as you sound so knowledgable.