if you selected a camera in your system that is not available or is used by another application, when you join the interpreter console it may take a little bit of time for the system to recognize the camera is not available. During that time you will not be able to click your microphone button. In several seconds you will receive a message that your camera is not available or occupied by another application. Please see this topic troubleshooting: http://interstaricp.com/forums/topic/message-the-camera-you-selected-is-not-available/