Utf-16 problems in the strangest of places

I'm getting strange crashes at times in our game (Running 4.3.7) in build. For example:

 ArgumentException: invalid utf-16 sequence at 4649196 (missing surrogate tail)..Parameter name: string - UnityEngine.Animator.SetBool (System.String name, Boolean value)

The line of code used to call this method is:

 animator.SetBool("Reset", false);

Anyone think of what might cause this? It's been working fine so far.