That worked for me. Turned off sharing, then back on. Does iTunes need to be open on the Mac to stream to the Apple TV? This is my 1st one. I assumed only my iMac had to be on. Looks like iTunes needs to be open as well.
I finally got it to work. I realized that itunes on the iMac was only 10.0 so I updated to 10.0.1, but still didn't work. I ended up turning off home sharing on the iMac then back on and the AppleTV started seeing the iMac. The MacMini hasn't been updated recently so I'm not sure what version of iTunes it's running.
Last night, home sharing started working suddenly. Today, homeshare is not working again. I think I may send this back. I did not sign up to be a beta tester. Maybe I will reorder it after they get the bugs worked out.
Think there maybe a homesharing bug. It worked for me the first time but after the Apple tv went to sleep I had to physically log out of iTunes, turn homesharing on and off and then it worked again