Recording and Playing back Streaming Audio and Video

Hi Folks...

I posted this in another forum too. I have this sample code from the e-book: "Learning Flash Media Server 3". The purpose of the code is to create a FLV. The code is not running as it should. When I click on the 'record' button, the label is to change to 'recording', that dosen't seem to happen and also when I click on the 'Stop Record' button, I get the following error:

"TypeError: Error #1009: Cannot access a property or method of a null object reference.
at MinRecord/stopRecord()"

I have my suspicion on a certain section of the code as the possible culprit, but I am not sure how to rectify it, I will post the entire code here so you guys can have a look.

package
{
      import fl.controls.Button;
      import fl.controls.TextInput;
      import flash.display.Sprite;
      import flash.net.NetConnection;
      import flash.net.NetStream;
      import flash.events.NetStatusEvent;
      import flash.events.MouseEvent;
      import flash.events.Event;
      //import flash.net.ObjectEncoding;
      import flash.media.Camera;
      import flash.media.Microphone;
      import flash.media.Video;

      public class MinRecord extends Sprite
      {
       private var nc:NetConnection;
       private var ns:NetStream;
       private var rtmpNow:String;
       private var msg:Boolean;
       private var cam:Camera;
       private var mic:Microphone;
       private var vid1:Video;
       private var recordBtn:Button;
       private var stopBtn:Button;
       private var textInput:TextInput;

       //Constructor
       function MinRecord ()
       {
       //NetConnection.defaultObjectEncoding = flash.net.ObjectEncoding.AMF0;
       nc=new NetConnection();
       nc.addEventListener (NetStatusEvent.NET_STATUS,checkConnect);
       rtmpNow="rtmp://192.168.0.11/vid2/recordings";
       //rtmpNow="rtmp:/vid2";
       nc.connect (rtmpNow);
       addMedia ();
       addUI ();
       recordBtn.addEventListener (MouseEvent.CLICK,startRecord);
       stopBtn.addEventListener (MouseEvent.CLICK,stopRecord);
       }

     private function addMedia ():void
      {
       cam=Camera.getCamera();
       cam.setMode (240,180,24);
       cam.setQuality (0,90);
       mic=Microphone.getMicrophone();
       vid1=new Video(cam.width,cam.height);
       vid1.attachCamera (cam);
       addChild (vid1);
       vid1.x=100;
       vid1.y=50;
       }

       private function addUI ():void
       {
       recordBtn=new Button();
       recordBtn.label="Record";
       recordBtn.x=100;
       recordBtn.y=50+(cam.height) +5;
       recordBtn.width=70;
       addChild (recordBtn);
       stopBtn=new Button();
       stopBtn.label="Stop Record";
       stopBtn.x=recordBtn.x+85;
       stopBtn.y=recordBtn.y;
       stopBtn.width=75;
       addChild (stopBtn);
       textInput=new TextInput();
       textInput.x=recordBtn.x;
       textInput.y=recordBtn.y + 30;
       addChild (textInput);
       }

       private function checkConnect (e:NetStatusEvent):void
       {
            msg=(e.info.code=="NetConnection.Connect.Success");
             if (msg)
        {
              ns = new NetStream(nc);
        }
       }

       private function startRecord (e:Event):void
       {
             if (ns)
             {
                   recordBtn.label="Recording";
                   ns.attachAudio (mic);
                   ns.attachCamera (cam);
                   ns.publish (textInput.text,"record");
             }
       }

       private function stopRecord (e:Event):void
       {
             recordBtn.label="Record";
             ns.close ();
       }
      }
}

My deduction is that the 'if' statement in the 'startRecord' function is not resolving to 'true' and hence the label is not changing to 'Recording'. Also I feel that the assingment to the variable 'ns' of type NetStream is not being done and hence in the function 'stopRecord' I get the above mentioned error message when I click on the stop button. How do I rectify these problems?