Missing objects upon save

Hi - 

I'm a novice user; I appreciate your patience.

I'm building a simple chart in AI, and when it's open, I see this:

But when I save the file, either in AI or as a pdf, I see this:

The disappearing object are up front, and they aren't hidden. If I move the text or the box from the top middle down and to the side a bit, they are visible on the saved document, but when I get close to the center, they disappear again.  I've tried saving everthing as the same layer with the same result.  

What am I missing?

Thanks for your patience and help!