Bone doesn't keep up with mesh

I have a model of an enderman from minecraft which consists of several large rectangular prisms, all separate of each other (same object, different mesh.) I rigged it all up and all the bones are control the correct block but when i rotate the arm 45 degrees the mesh rotates about 90 degrees. what is wrong?

check to see if there are multiple armature modifiers on the mesh. Make sure there is only one.

Thanks got it!