Display Log Off checkbox missing

Some of our installations of XP Pro are missing the Display Log Off checkbox as an option in the Advanced Start Menu Options list of the Customize Classic Start Menu. Could it have something to do with the way XP was initially installed or the way users are created? The inconsistency makes me worry there may be other quirks we just haven’t noticed yet. I’d rather not have to be checking for this and editing the registry to include the Log Off button on every computer we roll out.