Snippet kitt decided around 10:54 on 21 January 2010 to publish this:
Plugging in a 30" HD to a MBP and striking a key on the USB connected keyboard doesn't wake the monitor, even though the MBP may detect two screens.
SYMPTOM: The Mac Pro does not wake the 30" ACD monitor. Unplugging the monitor's Firewire and USB connections at the back of the computer wakes the monitor wake up. SOLUTION: Disconnect the 30" ACD monitor's Firewire and USB cables from the back of the Mac Pro. If necessary, disconnect your mouse from the back of the 30" ACD monitor and connect it to the front USB port of your Mac Pro. Open System Preferences. In System Preferences, open Energy Saver. Move the slider "Put the display(s) to sleep when the computer is inactive for:" Don't return the slider to the original position. In System Preferences, click on "Show all." Close System Preferences. Connect the 30" ACD monitor's Firewire and USB cables into the back of the Mac Pro. If necessary, connect your mouse back into the back of the 30" ACD monitor.