http://www.gamespot.com/news/2004/08/16/news_6104954.html
The day before Valve starts pre-loading Half-Life 2 assets onto its Steam network, it appears the publisher may have made an embarrassing mistake. Several Web sites--most prominently HL2World.com--have reported that Valve accidentally released a file containing all of the dialogue from Half-Life 2 when it distributed the Counter-Strike: Source beta to Cyber cafés last week.
According to reports, the dialogue is embedded in a .gcf file sent out along with beta. Apparently, it was included for closed-captioning purposes, and was overlooked because .gcf files arent meant to be opened. Obviously, it was not meant for public eyes and contains numerous spoilers about the game, including its (surprising) ending.
However, despite reports, the Half-Life 2 dialogue leak is officially unconfirmed. Valve did not respond to requests for comment as of press time, and has not made any announcements regarding the alleged leak.