Ill eventually try to help on SDK but as I know nothing about doing so it would require another several week distraction for me to learn what's going on.
I suspect there is some obscure buffer being read somewhere that shouldn't be, but that's just a guess based on my experiences with the importer not being able to distinguish between unused materials or textures sitting in a drop down list and those that are linked to an object. Unlike the Ogre exporter which seems not to have a problem doing so.
I find myself having to backtrack a lot and clean up unused things when using the importer because of it.
I'm really not partial to relying on Ogre (even though it works best) since its not open source anymore, we have to rely on others not associated with the Ogre developers to update the blender script, and its quite expensive.
You did confirm its not something I am doing to cause it, at least not something that's blatantly obvious.