We have recently switched our application to use savetoxml / loadfromxml instead of  the binary form.  However, it seems that any new images we add to our diagram are saved differently with a black background instead of a transparent one.  Existing images that were on the diagrams before (and loaded with the diagram) are still saved correctly, but any new ones have this issue.

We can see in the XML document that the newly added images are saved differently, even though they are originally from the same source file that the existing ones are.  Can you think of a reason that SaveToXml would cause us the transparency in our images to turn to black?