Use snd_async_fullyasync 0 to turn it back off.
We're looking into the problem, but it would help to know if this solves it for you.
Thanks,
Rick
Valve
Copy all of the *.gcf files from your SteamApps directory to the new pc where you want steam installed. That's what is downloaded when you are "preloading" caches.
Rick
Valve
Guys, try renaming your "source engine.gcf" to something else like "_source engine.gcf". Run steam and it will reload that file. Let me know if it solves your problem. The cache file is about 68MB.
Thanks,
Rick Ellis
Valve