This is a fault that has caused me much lost time; and yet it is so specific and obtuse I'm not sure anyone else will have the problem.
The fault manifests as PowerPoint crashing when using the Publish Command; specifically during (or immediately after) the compiling of audio.
After a number of days I've identified the problem - it was caused by having a Grey Scale PNG file as the Presenter Image.
Grey Scale JPEGs aren't a problem.
Colour PNGs aren't a problem.
Grey scale PNGs for the Presenter Image causes PowerPoint to crash consistently, magnificently and irretriveably every time you try and publish.
I've included a copy of the image that caused the issue. I've since tested using a variety of formats in colour and grey scale and it seems only Grey Scale PNG images have the issue.
BTW - the grey scale image was created in Photoshop CS5 using the Mode Command whereby colour information is discarded; I assume that in that process some vital element of information is lost that makes the file unreadable by the publish process and creates the crash.