They are too high a resolution for Apple TV. You will need to re-export them in AppleTV format using QuickTime Pro or a media encoder like MPEGStreamClip. This is detailed in the FAQ
BTW, do you know where Jeff got that wine aerator gizmo? I've looked for one locally and can't find it. It was very cool.
Now I'm off to Alaska (Denali Park followed by a cruise down the coast to Vancouver) for the next 2 weeks. I have your LR 2 tutorial to keep me occupied on the plane ride and LR2 loaded on my MacBookPro.
North Wales, PA