UPDATE: It’s back online.
UPDATE: All fixed. According to a post on Bungie.net, “The online team tells me the source of the problem was rooted out, physically destroyed, and tossed into a dumpster. Again, apologies for the early morning hiccups.”
ORIGINAL STORY: Halo: Reach is suffering a mysterious matchmaking outage, developer Bungie has confirmed.
A post on the developer’s official site explains that it doesn’t currently know the cause of the problem but is working hard on a fix.