i see a similar effect with my cube.
It is obviously a neon lamp which i switch off/on.
That produces a trigger in the electrical power line.
This makes my cube wake up, LCD or not.
Maybe you have a similar effect.
My 17" Studio Display shows the following symptom. It falls asleep after the time set in my Energy Saver Panel, but for some reason it wakes up at night, possibly due to activities of my G4, which never sleeps at night.