Andrew,
Thanks for pursuing this. I initially wrote because I had had the problem (printing a trifold brochure) in the past & on this occasion had tried everything to resolve it. Subsequently, i shut down my computer & when I tried again the next day, it worked! I don't know what causes the problem, nor what fixes it, but it is fixed at the moment.
I have had a similar problem printing a portrait document (a sign in sheet). I say similar because I don't know if this is a bug or not. After numerous attempts to get a 1 page document to print 2 copies back-to-back w/long edge binding, I had no luck. So I copied the document so that it is now a 2 page document. With a 2 page document, I can print w/long edge binding and it works fine.
So at the moment, unless it happens again, I'm all set. Thanks again for your offer of help.