http://bugs.winehq.org/show_bug.cgi?id=23516
--- Comment #5 from 3vi1 winehq.org@eternaldusk.com 2010-10-17 08:40:20 CDT --- I've been noticed this same bug yesterday in Counter-Strike: Source. I haven't really played it for more than a moment or two since they switched to the Orange Box engine, so I assume that's when it began happening.
As a workaround, snd_restart from the console window will get the sound going again... but you'll probably get shot while doing that. :)