Amaya Seems to loose MathML on save/re-open

I have several documents developed in Amaya using MathML (brilliant). 
However, I am finding that when I save the document, shutdown Amaya and 
then come back later to edit the document again the MathML disappears.

On loading the source has the MathML but it does not get rendered (it is 
OK in a browser - I use FireFox).

When I save the re-loaded document (after e.g. adding a single space 
character) the MathML disappears from the HTML source. My source 
directory contains all the style files needed.

I have attached a sample of before and after reloading.

What am I doing wrong?

Thanks

Nick