At approximately 9:20pm Pacific Daylight Time, folks on the Bungie.net forums began reporting that it was hard to get matches in Halo 3.
Instead of finding players, it would just restart the search. Pictured is the status message everyone seemed to be getting.
Whatever the problem is, it seems to have spread to LIVE (or vice-versa) as it's currently borked. So, we know, you can stop sending us emails letting us know. Microsoft probably knows, too.
Some people (Luke Plunkett, for example) are reporting that it's finally come back for them. What about you?