Hi Jambe - are you possibly trying to save curve objects?

The .3ds file format doesn't support curves, only polygon mesh objects. MoI will convert any surface or solid objects into polygon meshes when you export, but if you only have wireframe curves in your model you won't get anything.

Also, for export make sure you have stuff selected - export is for saving out only a subset of the current model instead of the whole thing, SaveAs will save the whole thing regardless of selection.

If you still have problems, could you please post the original .3dm file here so I could take a look?

- Michael