Updates to the Source SDK have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:

New Features

• Visual Studio 2005 Support for SDK Code
  
• Spectate Mode Added to Half-Life 2: Deathmatch

Bug Fixes

• Faceposer Crashes When When Trying to Extract or Add a .txt File
  
• Lag compensation added back into Half-Life 2: Deathmatch