Branching Issue

I've created a project in Articulate '09 and have a branching issue.  I've looked around the forums and haven't found anyone having quite the same issue I am. 

I have several sections with branching where learners are given one slide that contains several "buttons" for them to choose from. When learners select a button, they are taken to a new slide. Once the content on that new slide is complete, the presentation branches back to the initial slide in the group and the learner selects a new "button". 

I have this type of interaction in this particular presentation in several places and it works like a dream...until you get to the last grouping.  In that group, the branching takes you back to the wrong slide-even though I have NO hidden slides in the PPT presentation AND the correct slide number for the return branching appears in the slide properties (i.e. If I look at slide 77, it's slide properties show that it's supposed to branch to slide 75 when the narration ends;  but when the narration ends, it goes back to slide 64 instead.). 

I've rebuilt the section twice trying to solve the issue, but that hasn't worked. I can't understand why it's only affecting this one section and none of the other ones. What can I do to fix this?

Thanks for your help.