A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
I'm guessing that this is the key phrase in your question: "I have been adapting a presentation I authored and used last year." You are probably stuck in some sort of compatibility mode. You can try doing a Save As to see if you can save it in the 2011 format. If that doesn't help, you might try creating a new presentation and inserting the slides from the old one with Insert > Slides from > Other presentation.