ATV 2 and " wake up on demand" fixed for me
This fixed it for me. Read this very very carefully
http://support.apple.com/kb/HT3774?viewlocale=en_US
I wish I had - particularly the bit about
Setting up Wake on Demand
To properly configure your network and devices for Wake on Demand, follow the steps below.
Setting up a Bonjour Sleep Proxy on your AirPort Base Station or Time Capsule
Install firmware 7.4.2 or later on your AirPort Base Station with 802.11n or Time Capsule to enable it to act as the Bonjour Sleep Proxy. Once installed, your AirPort Base Station or Time Capsule will make itself available as a Bonjour Sleep Proxy to other devices on your network with no other configuration necessary.
Setting up a Mac with Sharing enabled
Only a Mac running Mac OS X v10.6 can Wake on Demand. New Macs ship with Wake on Demand enabled by default, but for some earlier Macs this option must be enabled using the steps below. Macs that have Wake on Demand enabled will occasionally wake for a brief time, without lighting the screen, in order to maintain registrations with the Bonjour Sleep Proxy. On some Macs, sounds from the optical drive, hard drive, or fans may be heard during these brief maintenance wakes.
Additionally, portable Macs with Wake on Demand enabled will only wake on demand if they are plugged into power and either the built-in display is open or an external display is attached.
To enable Wake on Demand on a Mac running Snow Leopard:
From the Apple menu, choose System Preferences.
From the View menu choose Energy Saver.
Select (check) "Wake for network access". Note: The "Wake for network access" option's text may differ depending on the capabilities of your Mac:
Wake for network access - Your Mac supports Wake on Demand over both Ethernet and AirPort
Wake for Ethernet network access - Your Mac supports Wake on Demand over Ethernet only
Wake for AirPort network access - Your Mac supports Wake on Demand over AirPort only
The wireless network you use with Wake on Demand should be the first wireless network in your list of Preferred Networks. The wireless network priority can be set within the Network pane of System Preferences using the following steps:
From the Apple menu, choose System Preferences.
From the View menu choose Network.
Select AirPort from the list of network interfaces.
Click the Advanced button.
In the Preferred Networks list, click and drag the name of your network that uses Wake on Demand to the top of this list.
Click OK to save the settings.
Powerbook G4 12, Macbook Pro 15" 2 Ghz, iMac G5,20,BT, 250GB, 1GB RAM,, Mac OS X (10.5.2)