Can you run an extension cord out to use the wall-wart on the lilliput? The regulator it comes with eats a volt or so, maybe your battery is a little low? It does odd things with low voltage, I've seen it be really dim, for instance.
Also, do the hard drives spin up? How is the Opus connected to the motherboard? Do you have both the jumper line from the Opus AND the ATX connector? Or just the ATX connector?