I can start iTunes on my Windows 7 desktop, and can browse it from my Apple TV 2. It works fine for a while, then randomly in the middle of the movie I'm watching it completely loses the connection and kicks me back to the Apple TV home screen. I have to restart iTunes to get it to work again.
This does not happen streaming from my MacBook Pro.
This also happens when Home Sharing between my MacBook and the desktop. I go to browse the desktop in iTunes to transfer something, it spins for a minute, then disconnects. Once again, a restart of iTunes on the desktop is required to get iTunes on my MacBook to see the desktop library again.
I've tried disabling the Windows Firewall to no avail.
Both iTunes and the Apple TV are up to date.
The network is solid with gigabit and a Linksys/Cisco E4200 with latest firmware. I had to disable WMM support to make AirPlay work.