NullReferenceException: object not in inspector?

Alright this has been driving me crazy for a while, And i'm starting to think i might have hit a bug or something.

Unless i'm mistaking, there is no reason i should be getting a null reference unless an object is selected in the hierarchy, right? i mean come build time (and it is giving me a nullreference on build) there's no such as a hierarchy. So there should obviously be no reason for a reference to work only when an object is selected in it, right? I don't understand what could be causing this, but i'm pretty sure this shouldn't even be happening.

My problem is with a GUI button dropping down a list of string variables. When the Manager object that contains the code is in the hierarchy it works perfectly, and even when i select another object while still leaving it on play. But as soon as i stop, and start again without having that object selected i'll get the error. if i select it will work again perfectly, even if i pause it and select the object so i can't figure out exactly what's causing the error. if i was on my computer i'd give a code example but that's impossible for me at the moment.

But am i really doing something wrong, or am i rgiht in that this shouldn't even be happening? thanks for any help!