[JS][CS5] Closing a session palette

Hi.

I have made a session palette that triggers certain scripts, but I need to be able to close the palette.  There is a red close button on the top left of the palette, but that has no effect.

I have written code for a close button, but that doesn't work either, although it did work once!

#targetengine "session"
...
var myDialog = new Window('palette' , 'xxx Formatter');
...
var Cancel = myPane.add("button",undefined,"Close");
...
Cancel.onClick = function (){
    myDialog.close();
    }
myDialog.show();

I can post the whole code if it helps, but above are the relevant lines as far as I can see.

The button is visible.

Cheers

Roy