Hi I received my Apple TV yesterday and tried to set it up. I have a Mac Book running 10.4 and a Mac Pro running 10.5. First I set up my laptop by going to preferences > Sharing > Firewall and turning on iTunes Music Sharing. I was able to synch the laptop with the Apple TV. I then tried to set up my Mac Pro, there is no preferences > Sharing > Firewall so instead I went to preferences > Security > Firewall and tried either allowing all incoming or adding iTunes to the selected applications. This allowed the laptop to play anything from the Mac Pro and the Mac Pro to play anything from the Laptop. However when I add the Mac Pro to Apple TV for streaming the Mac Pro appears grayed out under computers and its contents will not appear in the Apple TV. Please help, I have tried everything and can not get it to work.