I play CoD:bo, BF:BC2, Minecraft, SC2, and Half Life 2 and other older games such as AoE expansion, etc. I can play my games with sound, except CoD:bo Multi-player. Why? Everything that I have tested besides that works. I am completely boggled.
I think i know why you have no sound,i had the same problem, go to your multiplayer menu,SETTINGS/SOUND..at the bottom right it should tell you what device is enabled for the sound,sometime it is simply the wrong device and you need to change it,you can go to your control panel..SOUND/MANAGE AUDIO DEVICES..to see what device is enabled for the speakers and or headphones,this device should be the same as your black ops sound device..good luck