I have just manged to narrow it down to something in the layout file that Mamewah doesn't like.. (even the older version).  The wierd thing though, if I tell MAMEWAH to use a specific default (current) emulator, it loads it fine! 
If I use MAMEWAH to switch to another, it crashes.. if I manually switch it in the MAMEWAH.CFG file, it loads it fine.
?!?!