JLabel not displaying

[Blake Minghelli]

I created a custom modal dialog class that will pop-up, run some Runnable task, and then go away once the task is complete. It's a very basic window containing a single JLabel that displays some informational message to the user, like "Retrieving data...". Here is the code:

class ModalDialog extends JDialog implements Runnable {
 
   private Runnable task;
   private JLabel label;
 
   public ModalDialog (Frame frame, String msg, Runnable task) {
      super (frame, "RT Message Viewer", true);
this.getContentPane().setLayout(new FlowLayout());
      this.setSize(200,100);
      label = new JLabel(msg);
      this.getContentPane().add(label);
this.task = task;
   }
 
   public void run () {
final JDialog dialog = this;
try {
SwingUtilities.invokeLater(new Runnable() {
public void run () {
dialog.show();
}
});
 
SwingUtilities.invokeAndWait(task);
} catch (Exception e) {
debug(
"Exception invoking task: " + 
e.getClass() + ": " + e.getMessage());
}
this.dispose();
   }
 
}
  

To use it, I am launching a new thread, something like this:

ModalDialog dialog = new ModalDialog(
  null, "Retrieving data...", new MyRunnableTask());
Thread t = new Thread(dialog);
t.start();  

The problem is this: The first time I launch a new ModalDialog, it looks perfect - the window appears with the appropriate message. However, in subsequent uses, the JLabel does not appear so the user just sees a blank modal window. The only difference I can see is that the first launch occurs within the constuctor of my app whereas the subsequent launches originate through the event thread (e.g. user clicked a button). However, since in both cases, I run the ModalDialog in a new thread, it doesn't seem like that should matter.

I have tried many things such as calling repaint(), validate(), launching new threads, etc, etc.
Does anyone have any suggestions?