Make sure the keyboard layout is on 'default' in the right corner, when in the setup screen. H2Vista does come with several keyboard layouts/mappings.

Also, this is considered 'Team Chat', but enemies can hear you as well. AndI think it's all based on distance. So if nobody is around, than they can't hear you.

The key to checking your mic is in the Lobby, or the post game results screen. Everyone's mic is on then.