Source SDK is updating...no 3d preview lighting yet...

from the news page:

Source SDK Update Released
June 18, 2007, 4:10 pm - Jason Ruymen
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Updates to the Source SDK have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:

Added a Maya 7.0 SMD exporter

Added source code for the Antlion Guard as an example of a quadruped

Added HL Modelviewer and phonemeextractor source code

Developer console now bound to the F12 key as well as the '~' key

Added response files to fix NPC's not talking bug

Finally updated the SMD exporter eh? If it's faulty, I'll still stick to Prall's SMD exporter : http://mitglied.lycos.de/prallvamp/