Parts of armature moving other parts of the model even though there's no weight paint there? Title pretty much says it all. My hand bone is moving parts of the lower stomach area, and even though I try to subtract all of the weight paint in the area, that part still moves regardless. Any ideas?
Try it with auto-normalize disabled.
But you have to be careful, as this could mess up your weights and you may need to normalize them again.

You can also try it with "Limit selection to visible" disabled.
This could help if you have overlapping meshes.