As was stated previously, this is the way it is meant to operate. you will also require this to run as you kick of aireplay-ng. It will show you the amount of IV data fragments collected and as such provide an indicator as to when you crack the key. By the sounds of it, you are working from the command line environment with a single session. Try typing startx to launch a window GUI session.
Alot of videos on WEP/WPA cracking available online to get an idea of correct usage
cheers,
n1p
nice addon. my quess would be that he is learning form a video, but those videos do not show (or say) the stop command so thats where the help is needed, justneedhelp: am i right?