THQ's sleeper subway hit, Metro 2033, was patched recently in support of the "Ranger Pack" DLC, but it appears the update clashed with how the game tracks Achievements. Conflicted reports suggest the patch prevents all Achievements in the game, or simply the ones from the Ranger Pack -- either way, it's still a problem in need of a correction. According to the official Metro 2033 Twitter account, the publisher has been aware of the problem since August 3, most recently acknowledging the situation on August 5 as something on Microsoft's end.
In a statement to Joystiq, a THQ representative said, "We are aware of some users experiencing issues with achievements for Metro 2033's Ranger Pack DLC. We are currently investigating this issue with Microsoft and expect to have a resolution shortly." The representative added that the company should have something more concrete to share in "the coming days."