I installed the Unity 3.3. package, and when I even try to load the sample screens I get the following error:
NullReferenceException: (null)
UnityEditor.SerializedObject..ctor (UnityEngine.Object[] objs) (at C:/buildslave/unity/build/artifacts/generated/common/editor/SerializedPropertyBindings.gen.cs:74)
 
This is the offending line:
atlasAssets = serializedObject.FindProperty("atlasAssets");
In SkeletonDataAssetInspector.cs
Any thoughts on how to fix?
  
 30 Jun 2016, 22:08
 
  Ok I did a clean removal of every file, reloaded unity and problem seems to have gone away.
I guess it was a Ghost in the code!