1. are you using IK? i think it is common and there is a way to resolve it, but i don't remember

2. what does a vert that is affected by something that it shouldn't be look like in the component editor?
if the weights have any value for the bone that is moving then you should expect to see the vertex move
when you soft binded did you have maintain max influences checked on? if you did then you won't be able to make a vertex not influenced by a particular bone you don't want it to be.