Slide does not generate a notes page

I was just flipping through the notes view of a presentation, and noticed that one slide in particular does not show up - there is only a blank page.
When I look at the same presentation in 'normal' (ie slides) view, it's present with no problem.

Any ideas?

Thanks,

Tony

One reason would be that it has an animation at the start, and you need to press a key to move forward?