We're in the middle of upgrading the servers that receive game stats from the Xbox - processing of new stats may be delayed while we switch to the new system, and a few games might even fall through the cracks. (They'll still count for rank, just won't be visible on this site.) Sorry for any inconvenience.
When we're done, we'll be running on shiny new servers that will also be running the Halo 3 beta and eventually Halo 3 itself.
Update 1: We're up and running on a brand new server. Tomorrow we'll bring a few more online for redundancy, but that's shouldn't affect anyone. To clarify, this was just a routine server upgrade, similar to when we upgraded the web servers a couple weeks ago, and isn't a hint of imminent changes in the beta status. For those who asked, this is simply the server that receives stats uploads from the xbox for display on bungie.net, it doesn't literally "run" the game.