Sry for not responding sooner to you before... (don't worry I don't forget-I have a whole folder of stuff to reply too-it's just that I never have the time...)
See some notes from this post down
/forums/zimlets/2189-yahoo-maps-doesnt-work-email-4.html#post58323
-Specifically the default cos & composing just a text email
Bug 20436 - Yahoo Maps Zimlet does not display map image.