First I'll have to come clean and admit that it wasn't actually me that did it. This is a problem that my mum is having with her iBook and has now become my problem for the weekend (I'm visiting🙂).
I tried resetting the screen resolution to different sizes to try and "trick" it into view but that didn't work. I also tried mad jew's suggestion to erase the "com.microsoft.powerpoint.plist" and that didn't get it back either🙁
It's really bizarre.
Thanks for the suggestions so far!😀