Sometimes on XBL Halo 3 my microphone doesn't show up?

[Katlin]

So you know when you're in the lobby and beside your name it will show a speech bubble, microphone, or nothing? Well sometimes mine shows my microphone which I always have plugged in, and other times it just shows a speech bubble and I can't talk. this happens a lot and I normally just turn off my console then turn it back on. any sugggestions of what might be wrong? everything is brand new by the way.

Thanks!