Hi Sergio, I haven't heard of this problem before... Can you make sure you don't actually have 2 copies of the object on top of each other inside of MoI?
It is hard to give you a definite answer without seeing the file though, can you please post the .3dm model file (or send it to me at moi@moi3d.com) so I can take a look and see if it is a bug or if it is duplicated objects in the file?