I keep my cab in standby mode most of the time. At the moment I tap the atx power switch to rouse it from sleep. The BIOS supports waking from USB as a mouse double click, but the mouse click buttons on my minipac do not wake it. The green LED stays on in standby, so I assume it's getting power.
Is this a question of how the minipac identifies itself to the system? HID headers and the like?