There's a new Steam Beta client available. To access the Beta, go to File -> Settings. On the Account tab press the Change... button to open the Beta Participation dialog. Then Select Steam Client Beta, and allow Steam to restart itself. Here are the specific changes:
- Fixed a case that could cause stats and achievements to be reset
- Show timestamps in both group and individual chats based on global setting
- Fixed a Steamworks api crash that was affecting Call of Duty: Modern Warfare 2
- Tweaked the connection fallback logic to be more robust