Unity NullReferenceException on Sprite import

Hi there, i'm trying to create a sprite in the simplest way I know: Drag into the project Asset folder the .dds image. Here is what the Unity (2D mode) console tells me.

Anyone has an idea? Or should I report it as a bug?

  NullReferenceException: Object reference not set to an instance of an object
     UnityEditor.SpriteUtility.GenerateDefaultSprite (UnityEngine.Texture2D texture) (at C:/buildslave/unity/build/Editor/Mono/Sprites/SpriteUtility.cs:276)
     UnityEditor.SpriteUtility.TextureToSprites (UnityEngine.Texture2D tex) (at C:/buildslave/unity/build/Editor/Mono/Sprites/SpriteUtility.cs:392)
     UnityEditor.SpriteUtility.GetSpriteFromDraggedPathsOrObjects () (at C:/buildslave/unity/build/Editor/Mono/Sprites/SpriteUtility.cs:206)
     UnityEditor.SpriteUtility.OnSceneDrag (UnityEditor.SceneView sceneView) (at C:/buildslave/unity/build/Editor/Mono/Sprites/SpriteUtility.cs:46)
     UnityEditor.SceneView.CallEditorDragFunctions () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1773)
     UnityEditor.SceneView.HandleDragging () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1804)
     UnityEditor.SceneView.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1284)
     System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)