I've experienced this on many computers, and one of the reasons is that someone using a chat spammer or certain hack sets off sound for the game. I know this because sometimes when I load up my hacks and set them, once they come into use no one can hear anything.
Are you using Windows 7? If so have you checked the volume mixer on the very bottom right hand corner when Combat Arms is up?
It doesn't matter what your OS you're running if the game isn't crashing.
Btw, to elaborate on Complixity's post, go to your volume mixer and make sure CA isn't muted. You have to have CA open to check ofc.
Member Since: 20/02/2011 Donator Since: 12/08/2011 Minion Since: 04/10/2012