MW3 for PC: How does the in-game voice chat work?

[Mr. Bad Example]

I know there's probably something simple I'm missing or not considering. But I can't seem to get the in-game voice chat to work. I've configured things in the OPTIONS menu for chat and I can hear others using it in-game. But when I press "Z" (the keboard command for voice) I see no indication that I'm speaking and no one can hear me. I'm using a Microsoft Lifechat LX-3000 USB headset and mic. It works fine in other apps (although I don't play many other games so I don't know if it works there). Any and all help would be appreciated. I'm surprised there isn't more documentation about this when I Google or Bing it.

[necktie444]

Same problme here

[ZanyScum]

Did you check if the game you are testing with has a binding for "z"?