QUOTE(c-2 @ Jan 24 2006, 04:53 PM)

are u both using port forwarding on your router ? .. are you on the same ISP ?
No, different routers and different ISPs. But he lives nearby (ping = 26ms).
I've experienced the same problem with other hosts, when I try to join their arenas, their xbox'es are "invisible" to my xbox. This could of course be caused by someone opening a private arena and not creating the game, but that is at least not the case when I'm hosting.
Maybe I should report this as a possible bug?