Blademaster pearls

I've been trying to make a necklace for a Naga model I'm doing. I copied the Blademaster's geoset to my model, but now I want the pearls to allways face the camera, like in the Blademaster or Priest models, so they don't appear as flat circles but as spheres. So what I've done is copying the Blademaster's Ball bones, assign them to the new created geoset, fix the geoset's matrices, and create pivot points for each pearl's bone by selecting the pearl's vertices with Oinkerwinkle's Vertex Modify program and using the "center of mass" tool.
So now I supposed everything was OK and it should be working, but the pearls are not moving. Can someone tell me what I did wrong or if I forgot something ?

Are the bones billboarded? If not, make them bilboarded.

Yes, they are. Is it the effect that makes them always face the camera (that's what I had been thinking, but I wasn't sure).

Right.

Do you mean that they don't move at all? If they don't move, then it might be that you need to assign the chest bone to be the parent of all the necklace bones.

Did the billboarding itself work/Do the necklace pieces rotate? If not, then post the bone and the matrices, I guess.