Soundbug

Have you tried reinstalling? I wouldn't know another fix other than updating your sound drivers.

There may be some sound-codec problem. Don't trust Windows to be working properly. It said my sister's computer sound was working fine too, but there was no sound at all. The fix then, was to download Realtec Hd-Audio and install that. Somehow the drivers had been corrupted in an update. But as your other games have sound, it must be some conflict with CrossFire. You should send a support ticket and see if the GM's can help.

As for Windows Update, don't trust it. I don't know how many times i have had to reinstall Windows, because Windows Update have made my PC crash.
Update, Please Restart, Restarting... An error has occured, Recover an earlier version of Windows, Starting Recover..., An error has Occured. Would you like to reinstall Windows?
After the last time, I updated Windows 7 as far as i could without having any problems, then disabled Update. Since then it has worked without problems. I'm feeling alot of dread, when im thinking about that i have to install Windows 10 next year. As it's Update are even more troublesome.