I've found that the model I'm using responds differently to D3D than OpenGL. In OpenGL, the character's arms twitch and move all over the place, whereas in D3D they stay pretty much stationary.
I think this might be related to the bug I reported earlier about getAbsolutePosition(), since in both cases funny things were happening with the weapons (the bone nodes weren't in the same place as the visual arms). Now both the arms and the weapons are seemingly in the wrong place.
Here's an example:
http://harkath.com/irrlicht/DirectXBug_OpenGL.zip