netStream information plz

the following code is a netStream on status if function however if i change createNetStream(this); to createNetStream(_root) or createNetStream(_level0) or createNetStream(_level0.clip0) then my NetStream doesn't get created ........why?


nc = new NetConnection();
nc.onStatus = function(info) {
if (info.code == "NetConnection.Connect.Success") {
createNetStream(this);

}
}