Over the New Year period we experienced an issue with some of the leader boards and stats for Xbox 360 titles. We have identified the issue, and have been working on resolving it.

What happened was not a result of a hack (or hacks) or anything else security related. This is a bug, plain and simple.

Edit: The issue is now fixed, and stats have been restored, with the exception of Geometry Wars:evolved. The team continues to work on that title's leaderboards.