I have two PCs running Windows 7 64-bit. I also have an iPhone 4. Both computers are wired into the same router, a Netgear WNDR3700, and are on the same network. The iPhone is wireless and also on the same network. Both windows machines are in the same homegroup. These devices can all easily communicate with each other over the network without issue. Every single network application, even Windows file sharing, is communicating between these devices except for iTunes.
Both PCs are running the newest 64-bit iTunes 10.5.3.3. I tried restarting iTunes, restarting the bonjour service, and restarting the computers completely. I tried uninstalling then reinstalling iTunes and bonjour on both machines. I tried disabling home sharing and enabling home sharing. I tried enabling and disabling windows firewall. I tried to use the iPhone remote app. Nothing works. The sharing icons never appear in the sidebar of either iTunes. The sharing icon never appears in the music app on the iPhone.
A few weeks ago, I think before some iTunes updates, it was working a little bit. If I restarted both iTunes they would detect, and I could stream for awhile. After a period of time it would just stop working and I could restart both iTunes to make it work again. Now it's just not working at all under any circumstance.