Error:Fixing reference to the runtime script in scene file!

Using Unity5.0.1f1 New AssetBundle System.

1: i have a animator StateMachineBehaviour scripte. and this script will build into one dll plugins.
2:Create a OverrideController and some state have the StateMachineBehaviour.
3:Build the overrideController into one assetbundle
4:create the character and set animator in runtime

The first time is ok,and all assetbundle has loaded will cached into static Dict. and all asset has loaded will cached into Dict too.

BUT! when Application.LoadLevel("new scene")
and then,Create the same character again. because the assets has loaded. so the error show:

Fixing reference to the runtime script in scene file!
UnityEngine.Animator:set_runtimeAnimatorController(RuntimeAnimatorController)


but i have test the Source code, this means the StateMachineBehaviour c# file is in Unity3D Assets.
and the same opeartion is all ok!