No I don't work for Apple, I work for state government. I got an email from this thread because I was subscribed back in January (page 6 this thread) when I was having an issue with my iTunes Library sharing no longer working. I went through the process of restoring my ATV2, Airport Ex and Qwest DSL modem settings to factory settings. Reconnected my computer's iTunes accounts to the Apple TV and it still didn't fix it.
This may sound odd but I had read elsewhere that about the same time Apple added WiFi syncing to iPhones instead of connecting them with a cable it broke the home sharing connection after awhile. The fix for me is explained here.
https://discussions.apple.com/thread/3679932?answerId=17385083022#17385083022
After my iTunes Library was again working for awhile, I did turn wifi syncing back on and it's still working.
We often jump back and forth between our "Music" iCloud AND our 2 computers iTunes Library accounts on our ATV2. The ATV2 just got a software update and I am now listening to some music and Bible audio files on it as I type this and have not had a problem this evening.
Here is my equipment and settings.
1. Qwest Actiontec M1000 DSL modem
Downstream Rate: 7168 Kbps
Upstream Rate: 896 Kbps
ISP Protocol: PPPoE
ATM Encapsulation: LLC Bridged
2. Airport Extreme (newest model) ethernet cable to DSL modem
Used Airport Utility 6.0 for setup
Station Software 7.6.1
Internet Tab: Using DHCP
Wireless Tab: WPA/WPA2 Personal Wireless Option Button:802.11n b/g compatible
Network Tab: Off-Bridge Mode, My DSL modem is feeding all the IP addresses to the Airport and devices.
Disks Tab: Enable file sharing CHECKED
3. MacBook (OS X 10.7.3) using Wifi
iTunes 10.6
4. PowerMac G4 tower (OS X 10.5.8) ethernet cable to Airport
(My media server always on and running iTunes)
iTunes 10.5.3
5. Apple TV 2 (ATV2) using Wifi
Software 5.0 (4099)
6. iPad2 using Wifi sync
7. Two iPhone 4 using WiFi syncing turned on again.
Hope something here helps someone.