I have the same exact problem and I can't figure it out, I've tried everything I can think of. I'm running version 10.0 SP4. Dynamic text doesn't honor an empty attribute as it is supposed to. I calculated adjacent pages using the toolbox tool. It is setup so that the text for adjacent pages that do exist works properly, it shows "See Page 2" in my case, for example. But for adjacent pages that are blank/don't exist it shows "See Page". If I define a value for emptyStr, it doesn't work. If I remove any preStr or postStr, it still doesn't work, it is just blank in Layout view. It doesn't even show [empty] in Layout view like the help describes.
I'm wondering if Ryan might have figured it out.