I have a Mac Pro 1,1 (Flashed to 2,1 with 2x 2.66 Quads and 32GB of ram) and I can send the wake up packet and have it work for around 30 seconds before it sleeps it self again and the packet will no longer work if you were to send it again. I have tried all the old tricks from lion and mountain lion but they no longer work. Yes i have wake on Ethernet enabled and I have disabled the lock screen to keep that from being an issue.