I have the same problem, but putting the objects into a new blendfile didn't work at all. I even deleted everything except the pure objects (texture, materials, images, armatures,...). But it didn't solve the problem.
Then I tried to export the objects with the internal OBJ-export funktion of blender. The export worked and even the import to octane, but the objects kept invisible in octane and I couldn't find any way to make them visible (even the materials appeared in the object node). There was a render going on, but nothing was to see except the backround (backround image or sky).
I used blender 2.65 and blender 2.66, both times the same problem!
Any further ideas...?
Win7 64Bit & ubuntu 64Bit / Intel i7 / 16GB RAM / GTX 580 3GB / blender 2.6x