Im also having this problem, I try to join Rooms with 20+ Users inside, but when I try to enter, an Empty Box appears with no users inside, so I immediately press B (cancel) when this happens because if I wait a few seconds, my XBOX will SHUTDOWN. Press B will save your xbox from Turning Off.
After pressing Cancel you can go back to LINK and try choosing a different room again... The Problem is, when I enter rooms with less than 10 users.. I dont see any HOSTS.
Why are there users inside a Room but when I go to Multiplayer System Link, I dont see any Hosts?