Major Nelson has posted an update to his blog indicating that Xbox Live matchmaking has now been fixed, though no explanation has emerged as of yet for the trouble. The man also known as Larry Hryb plans to explain the technical problems on his next podcast. I expect the internet will produce some answers before then, but I'd like the inside scoop.
I would love to say that the sheer magnitude of the PX360 Gears party crashed the Xbox Live servers, but I doubt that is the problem. Some readers would like to know why even their single player games started to act up last night. Could it be that games like Gears routinely check Live for some reason that prevents the campaign from playing smoothly? Any tech heads out there want to make a guess?