Particle Objects are Visible but don't Render

Hi, I have created some particle objects using Dupliverts, then rendered the scene and all of the particle objects were visible including shadows. I then saved the file.

Upon reopening the scene I can see the objects in “Particle Mode” but when I render the scene all I see are the shadows cast by the objects, but not the objects themselves.

I thought maybe a render icon was not selected but I’ve checked and all render icons are selected so I don’t know why my objets are not showing up.

Any ideas?

pg