How can I fix the weight painting? What's going on here? 



I had done all my weight painting but I ruined it by using symmetrize. As you can see in the pic, the selected bone is moving the other arm too. I already made sure it's not weight painted and I fixed the vertex group to not include that arm. What else do I need to fix? 

Also, can anyone give me a quick way to mirror weight painting already applied to one side to the other? I asked it here a while ago: 

https://blender.stackexchange.com/questions/47671/how-to-mirror-weight-painting-already-applied-to-one-side

Thanks
It was a simple solution. I had to remove the weight painting from areas connected to the upper arm too, not just the upper arm. When I symmetrized, it copied all the weight painting on my right to left but kept it assign to the same bone/vertex group.