http://www.steampowered.com/v/index.php?area=news&cc=US
Updates to the Source SDK have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:
Fixed problem with building cubemaps for TF2, Ep2, and Portal maps
Added missing models and textures for Hammer and Model Viewer. This addresses two crashes
Fixed problem loading 'FileSystemOpenDialog.dll' in Hammer and Model Viewer
Changed the game configuration logic such that only Orange Box games are available in the active games list when the SDK is set to use Orange Box tools. Only pre-Orange Box games are available when the SDK is set to use the Ep1 tools
Temporarily disabled Hammer Lighting preview modes until compatibility issues can addressed
