Animation state machine not playing animation on triggered state

Hi there! I've been having an immense amount of trouble wrestling with the Unity 4.3 Animator component. I'm trying to implement a four-directional animation with two states each: idle and walking. I've connected the Idle Up and Move Up states with a StartMove and StopMove trigger and, while it does change states as I would expect, it does NOT play the animation that should be playing on that state. Is there something fundamental I'm missing about the transitions and/or their conditions? Any ideas at all? Thanks!