Import the attached .avi file in Unity. Notice that the only error you get says that Unity could not read the file. But you have no idea why or how to fix it.

Importing the same video file in Unity 4.3 gives the following error:

"Could not find QuickTime video codec for 'XVID' on your computer. Please install this codec and reimport the movie.

UnityEditorInternal.InternalEditorUtility:ProjectWindowDrag(HierarchyProperty, Boolean)
UnityEditor.DockArea:OnGUI()
"

Now that is much better. I know what I have to do now. This is a regression from Unity 4.3, since the helpful part of the error is not displayed anymore.

This is a Windows only issue. On mac the error is reported as expected.