http://www.steampowered.com/index.php?area=news
A small number of Half-Life 2 customers have been experiencing problems while playing the game, and we have traced these issues to corrupt Steam cache files. We've released a Steam update to help resolve these issues. If you have been experiencing problems such as crashing during gameplay or startup of Half-Life 2, please restart Steam and then click on one of the links below. Steam will then automatically verify your cache files. The verification process will take roughly five minutes to complete.
A small number of Half-Life 2 customers have been experiencing problems while playing the game, and we have traced these issues to corrupt Steam cache files. We've released a Steam update to help resolve these issues. If you have been experiencing problems such as crashing during gameplay or startup of Half-Life 2, please restart Steam and then click on one of the links below. Steam will then automatically verify your cache files. The verification process will take roughly five minutes to complete.
But glad the others can finally play and have flawless sounds as well 
