.focus not working with dialog boxes in jquery UI

Question

Hi, I'm trying to set focus for a text box, after validating it. The form is loaded within a Jquery UI dialog. I found that the .focus is not working in it. Any ideas how to fix this ?

I have been tried this :

 $("#txt_usernameReg").blur(function(){
 setTimeout(function() { $("#txt_usernameReg").focus(); alert('settimeout'); }, 50);    });
});

The alert works, but the focus does not.