Hi,
in reply to this thread: http://extjs.com/forum/showthread.php?t=7964. I've search in the Ext 2.0 forum but I haven't found nothing.
So, I want to share my personal solution to solve the problem relative to MessageBox... any suggestion or improvement is appreciate.

PRE: Attach a document event listener onkeypress that handle the tab key press. Bind to this function an object that contains your Ext.Window (yourMessageBox.getDialog()) and a variable used to store the current focused button
POST: This is the code of the function called by the event handler:
PHP Code:

function ensureModalWindow(){
    
this.currentFocused = ((this.currentFocused+1) % 4);
    while (
this.buttons[this.retrieveButtonType(this.currentFocused)]===undefined){
        
this.currentFocused = ((this.currentFocused+1) % 4);
    }
    
this.winbox.defaultButton this.currentFocused;
    
this.winbox.focus();

This is the code of retrieveButtonType:
PHP Code:
retrieveButtonType: function(btn_index){
        switch (
btn_index){
            case 
0:
                return 
"ok";
            case 
1:
                return 
"yes";
            case 
2:
                return 
"no";
            case 
3:
                return 
"cancel";
            default: 
//not used
                
return "";
        }    
    }, 
this.buttons is an object like this:
PHP Code:
{ok"label for button ok"cancel:"label for cancel"
this.currentFocused is the index of the current button that has focus. Initialize it when creating your MessageBox, like:
PHP Code:
var msgbox Ext.MessageBox.show({
           
title:this.title,
           
msgthis.message,
           
buttonsthis.buttons
           
fnthis.boundProcessResult,
           
iconthis.messageType
       
});
this.winbox msgbox.getDialog();
       
this.winbox.on('hide', function(){
                
/* remove tab keypress handler*/
        
});
       
this.currentFocused this.focusedButton;
       if (
this.focusedButton!=-1){ // set default button with focus
               
this.winbox.defaultButton this.focusedButton;
               
this.winbox.focus();
       } 
Remember to remove event listner for tab when close the MessageBox.The solution is only applicable with MessageBox... because you know all kind of buttons you can display.

I hope it was clear!

Sorry for my english.