Home Sharing on ATV broken with Mountain Lion

I use Home Sharing almost daily with my third gen Apple TV but, since I updated my MacBook Pro (late 2011) to Mountain Lion, it just doesn't work. I have Home Sharing turned on in my iTunes account and it is also enabled on my ATV, they just don't communicate. Has anyone else had this problem? Is there something I can do to get it back up and working? Thanks for your comments.

Cheers