I've inherited a presentation from someone that I have to tailor and use in a day or so. Somehow, about 0:10 after I start the slideshow, it goes to a black screen as if I've hit 'B'. It's definitely not just a black slide, but the screen has actually gone black. To bring the screen back, I have to hit 'B' twice. The slide will not have advanced when I do this. I've searched high and low. Anyone have any thoughts on what setting might be responsible?

Thanks. This is with PowerPoint 2010 32-bit on Windows 7 64-bit.