Array = null when passing as parameter

Straight to the point. The following code is in a script that executes before all other scripts:

public static AudioClip[] FootstepSounds;

void Start()
    FootstepSounds = Resources.LoadAll("Sound Library/Footstep Sounds", typeof(AudioClip)) as AudioClip[];

The above always worked for me and the path is correct. I then use this Array in another script like this:

AudioClip currentAudioClip;
void Footstep() // I'm using this as a Mecanim Event on a walk animation
    Debug.Log("List null? -> " + SourceScript.FootstepSounds == null); // returns "List null? -> false"
    Debug.Log("List length -> " + SourceScript.FootstepSounds.Length); // NullReferenceException

    // of course NullReferenceException at the following line too
    currentAudioClip = SourceScript.FootstepSounds[Random.Range(0, SourceScript.FootstepSounds.Length)];

The compiler tells me that the collection is not null, so it must be the elements, which were obviously provided inside the source script. Does anyone know what’s going on?

Thanks for your suggestions, OncaLupe. It’s weird but it looks like the only way to make it work, is to replace all ‘AudioClip’ occurrences with ‘object’ and cast to ‘AudioClip’ in the final assignment at line 8 in the second script.