I'd bet dollars to doughnuts you need to flip normals on your emitters. Octane only emits from one side of the normals.
I've requested that we be able to flip in octane, or ignore in octane and have it emit from both sides, so we'll see if that happens anytime soon, however in the mean time, you just have to fix in the modeling application.
(I think Blender struggles with getting normals correct)
CPU - i7-950 3.06 Ghz, 24GB Ram, Win7 x64, 2 display monitors, GeForce GTX 580 3GB Classified. I'm glad to say I LOVE OCTANE!