Are all emfs not the same?

Some emf files display correctly in our GoDiagram application and others don’t.
Emfs created by Paint Shop Pro display fine, but those created by Illustrator and Publisher do not display (the image is blank/null).
Any thoughts on why this is happening?

No idea. GoDiagram’s GoImage.Paint method just calls .NET’s Graphics.DrawImage(Image, RectangleF) method.
So it’s likely that that failure will happen for any .NET application, not just one using GoDiagram.