Tried all of the usual options and none of them work, I get the same old cracks, pops and disappearing sound as always BUT I can get perfect sound under the following circumstances:

1. If I run in a window.

2. I have 2 accounts on my PC. If I log on to one and then shift-right click steam, select "Run as different user" and open it using the login detail of the other account, it works fine.

Just thought I'd share as these are the only 2 remedies I have found that work, even if they make no sense at all! ATI 5770, Phenom II 720BE, XFi Gamer, Win 7 64 Home Premium, 6Gb RAM. They all suggest that the sound drivers are NOT the problem and that something else is causing problems.

Can someone else let me know if the above work for them?