JMF: Problem with Controller Realization

Question

I have a problem with the realisation (Player.realize();) of my Player that receives RTP Video Streaming: The realize(); method never ends. I've implemented ReceiveStreamListener and ControllerListener. When a NewReceiveStreamEvent occurs (which does fine) the player gets created:

public void update(ReceiveStreamEvent event) {
 ReceiveStream stream;
 if(event instanceof NewReceiveStreamEvent){
  stream = ((NewReceiveStreamEvent)event).getReceiveStream();
  DataSource datasource = stream.getDataSource();
  Player player = null;
  try{
   player = javax.media.Manager.createPlayer(datasource);
  }
  catch(IOException e){
   e.printStackTrace();
   System.exit(1);
  }
  catch(NoPlayerException e){
   e.printStackTrace();
   System.exit(1);
  }
  if(player != null){
   player.addControllerListener(this);
   player.realize(); //takes forever...
  }
 }
}

It is said in the JMF DOC that realize() either ends with the player in either state realized or unrealized

A TransitionEvent occurs which informs me that the player went to the state: realizing. But a second TransitionEvent which says that it is realized or unrealized does not occur.

Anyone have a clue whats going on?