NetConnection unhandled NetStatusEvent

Occasionally I'm getting an unhanded NetStatusEvent when using NetConnection to connect to a Red5 server:

Error #2044: Unhandled NetStatusEvent:. level=error, code=NetConnection.Call.Failed

This is how I am connecting (the only place where NetConnection.connect() is called):

public function Connect(callBack:Function = null):void 
{
    if (IsConnected())
    {
        if (callBack != null) 
        {
            callBack.call();
        }
    }
    else // Not connected
    {
        netConnect.addEventListener(NetStatusEvent.NET_STATUS, function(e:NetStatusEvent):void
        {
            // OnConnect called whenever there is a net status event
            OnConnect(e, callBack);
            netConnect.removeEventListener(NetStatusEvent.NET_STATUS, arguments.callee);
        });

        try
        {
            // Attempt to connect to Media Server
            netConnect.connect(MEDIA_SERVER_URI, true);
        }
        catch(error:Error)
        {
            logger.LogError("NetConnection.connect threw an exception.", error);
        }
    }
}

I am adding an event listener for NetStatusEvent.NET_STATUS. How is it possible that sometimes my listener called?

You're removing your listener in your NetStatusEvent handler. You should keep it until the connection is closed. This is why NetStatusEvent is only handled once before its listener is removed. Any other than first event will throw that error.

So remove netConnect.removeEventListener(NetStatusEvent.NET_STATUS, arguments.callee);

NetConnection dispatches that event quite a lot, depending on what is happening. You have to handle the event until every time. For a list of possible values of the info property visit this Link. There's also a little example of how to handle the event at the end of the page.