ExecuteInEditMode not working in some scripts

I am using @script ExecuteInEditMode(); to update object sprites in the editor when I select a new enum dropdown value. This was working quite well until at some unknown point, it stopped working for almost every script. Is there a setting or object type that would keep this from executing in certain scripts but not others? I've searched every help topic i can find with no success.

The test code that works in some scripts and not others:

 #pragma strict 
 @script ExecuteInEditMode();

 function Awake(){
      Debug.Log('Update');
 }
 function Start () {
      Debug.Log('Start');
 }
 function Update (){
      Debug.Log('Update');
 }