Hmm, are you using a language file other than one of the five standard languages (English, German, Polish, Italian, Japanese) that come with 1.3.6? Because I can see that what you describe happening when $LANG24[11] is empty ...
If so, then sorry about that - sanity checks have been added to all the other admin pages to prevent that from happening, but it seems story.php slipped through the cracks ...
bye, Dirk