Since its release in November, Halo: MMC has had some serious issues, mainly in the multiplayer side of the game. Unranked matches, server lag and matches unexpectedly quitting are just a few of the issues players have to put up with. 343i told players that the update they released just before Christmas should resolve these issues but it only seems to make things even worse.
Another issue is the achievements. Often through out the campaign or multiplayer, achievements will not unlock. More often than not they will appear in your inventory once the servers regress at 00:00 PST but there are reports of players having no such luck and even having their stats and achievements drop to 0% with no sign of recuperating. As much as it is a great game, it’s very hard to focus on all its glory while dealing with so many issues!