Damn, I tried to upload a .car file with a similar hand that I have rigged. I have a cartoon hand similar to that one rigged with bones (and ik, as they aren't attached to a body I figured I might as well use ik, even if people often don't recommend it for hands). Anyway, open the VM, select the polygons that don't move correctly, then open the bones tab in the properties. Then change the bone influences, remove the bones you don't want to affect it.