Video doesn't play properly in some conditions and works great in others (case16899)

[hou1b]

I have 3 conditions that play the same 52 seconds long .mov video. It works great in one condition but it doesn't play properly in the other 2 conditions. When it doesn't play properly, I see a black square in the middle of the screen where the video is supposed to be playing and a tiny square clinging to the top edge of the screen, playing the video. The audio is fine. The video file is in the same folder with the .exp file. Could anyone tell me what's going on here?

Thanks!