I've found a bug related to the 'Instance Master Hidden' parameter found on the Rendering tab of the Visibility property page.

This flag does not work with 3delight (as it does with mr). If set to true, the mesh is not rendered for any of the instances; all duplicates of the mesh vanish.

Setting the flag to false does not make the instances visible again. But shutting down and restarting Softimage refreshes the scene and objects (and instances) render once again.

Hope this helps.