Default_value not working for Radio Buttons in Ajax Callback

I have copied and pasted all the relevant form definitions for this radios problem:

  //Get the addresses that this user has under their uid from the database
  $result = db_query("SELECT add_id, add_First_Name, add_Last_Name, add_Address, add_City, add_State, add_Zip_Code, add_Country
    FROM {addresses}
    WHERE uid = :uid", array(
    ':uid' => $node->uid
  ));
  
  //Fieldset for the addresses, this is being themed, as we want each address radio button
  //to be followed by its own edit and delete buttons
  $form['addresses'] = array(
    '#type' => 'fieldset',
    '#theme' => 'theme_Addresses',
    '#prefix' => '<div id="Addresses_wrapper">',
    '#suffix' => '</div>',
  );
  
  //Check to see if there are any addresses for this user
  if ($result->rowCount()) {   
    
    //Initialize the addresses array to enter all the available addresses for this user
    $addresses = array();
    //Just a counter to keep track of the default value for the radio button, basically the first address should be selected
    $count = 0;
    
    //Now store all the addresses available for this user in the addresses array
    foreach ($result as $address) {
      
      $addresses[$address->add_id] = '<b>' . $address->add_first_name . ' ' .      
      address->add_last_name . '</b><br>' .
      $address->add_address . ',' . '<br>' .
      $address->add_city . ',' . '<br>' .
      $address->add_state . ',' . '<br>' .
      $address->add_zip_code . '<br>' .
      $address->add_country;
    }

        //Add the edit button for this address
        //Also adds the ajax callback, basically this would be like entering a new address only
        //that we retrieve the address values from the database and insert it into the textfields as the default_value
        $form['addresses']['editaddress' . $address->add_id] = array(
          '#type' => 'button',
          '#value' => 'Edit',
          '#name' => 'Edit Address' . '-' . $address->add_id,
          '#ajax' => array(
            'callback' => 'EditAddress_ajax_callback',
            'wrapper' => 'EditAddress_wrapper-' . $address->add_id,
            'method' => 'replace',
          ),
          '#prefix' => '<div id="EditAddress_wrapper-' . $address->add_id . '">',
          '#suffix' => '</div>',
          '#limit_validation_errors' => array(),
          '#submit' => array(),
          '#weight' => 20,
        );
        
        //Add the delete button for this address
        $form['addresses']['deleteaddress' . $address->add_id] = array(
          '#type' => 'button',
          '#value' => 'Delete',
          '#name' => 'Delete Address' . '-' . $address->add_id,
          '#ajax' => array(
            'callback' => 'DeleteAddress_ajax_callback',
            'wrapper' => 'DeleteAddress_wrapper-' . $address->add_id,
            'method' => 'replace',
          ),
          '#prefix' => '<div id="DeleteAddress_wrapper-' . $address->add_id . '">',
          '#suffix' => '</div>',
          '#limit_validation_errors' => array(),
          '#submit' => array(),
          '#weight' => 20,
        );
        
        //Save the first address id, to make it as the default value for the radio buttons
        if ($count == 0) {
          $default_value = $address->add_id;
        }
        $count++;
    }
     
    //Add all the addresses to the radios button
    $form['addresses']['radios'] = array(
      '#type' => 'radios',
      '#title' => '',
      '#options' => $addresses,
      '#default_value' => isset($user->data['NewAddress']) ? $user->data['NewAddress'] : $default_value,
    );
		
	//Display the fields when the 'Add_Address' form state is 1
	if ($form_state['Add_Address'] == 1) {
    
    //Fieldset, container for the new address fields
    $form['newaddress']['fieldset'] = array(
      '#title' => t("Please enter your details"), 
      '#prefix' => '<div id="NewAddress_wrapper">', 
      '#suffix' => '</div>', 
      '#type' => 'fieldset',
    );
    
    //Display the fields to enter the new address information
    $form['newaddress']['fieldset']['first_name'] = array(
      '#type' => 'textfield',
      '#title' => t('First Name:'),
      '#size' => 30,
      '#maxlength' => 128,
      '#required' => TRUE,
      '#default_value' => isset($edit_address) ? $edit_address->add_first_name : '',
    );
    
    $form['newaddress']['fieldset']['last_name'] = array(
      '#type' => 'textfield',
      '#title' => t('Last Name:'),
      '#size' => 30,
      '#maxlength' => 128,
      '#required' => TRUE,
      '#default_value' => isset($edit_address) ? $edit_address->add_last_name : '',
    );
    
    $form['newaddress']['fieldset']['streetaddress'] = array( 
      '#type' => 'textfield',
      '#title' => t('Address:'),
      '#size' => 30,
      '#maxlength' => 128,
      '#required' => TRUE,
      '#default_value' => isset($edit_address) ? $edit_address->add_address : '',
    );
    
    $form['newaddress']['fieldset']['city'] = array(
      '#type' => 'textfield',
      '#title' => t('City:'),
      '#size' => 30,
      '#maxlength' => 128,
      '#required' => TRUE,
      '#default_value' => isset($edit_address) ? $edit_address->add_city : '',
    );
    
    $form['newaddress']['fieldset']['country'] = array(  
      '#type' => 'select',
      '#title' => t('Country:'),
      '#options' => $countries,
      '#required' => TRUE,
      '#default_value' => isset($edit_address) ? $edit_address->add_country : 1,
    );
    
    $form['newaddress']['fieldset']['state'] = array(
      '#type' => 'select',
      '#title' => t('State:'),
      '#options' => $states,
      '#default_value' => isset($edit_address) ? $edit_address->add_state : 0,
      ),
    );  
    
    $form['newaddress']['fieldset']['zipcode'] = array(
      '#type' => 'textfield',
      '#title' => t('Zip Code:'),
      '#size' => 10,
      '#maxlength' => 128,
      '#required' => TRUE,
      '#default_value' => isset($edit_address) ? $edit_address->add_zip_code : '',
    );

    //Add the submit button to save the new address in the database and update the address list with the new address added
    $form['newaddress']['fieldset']['save'] = array(
      '#type' => 'submit',
      '#name' => 'Add New Address',
      '#value' => 'Save',
      '#ajax' => array(
        'callback' => 'NewAddress_Save_ajax_callback',
        'wrapper' => 'NewAddress_wrapper',
        'method' => 'replace',
      ),
      '#submit' => array('NewAddress_submit'),
      '#validate' => array('NewAddress_validate'),
    );
    
    //Add the cancel button to cancel the "Add New Address" form
    $form['newaddress']['fieldset']['cancel'] = array(
      '#type' => 'button',
      '#name' => 'New Address Cancel',
      '#value' => 'Cancel',
      '#ajax' => array(
        'callback' => 'NewAddress_Cancel_ajax_callback',
        'wrapper' => 'NewAddress_wrapper',
        'method' => 'replace',
      ),
      '#limit_validation_errors' => array(),
      '#submit' => array(),
    );
    
  }
  
  //Else, add the enter new address button
  else {
    //Add a button to enter new addresses
    $form['newaddress']['addnewaddress'] = array(
      '#type' => 'button',
      '#name' => 'Add New Address',
      '#value' => 'Add New Address',
      '#ajax' => array(
        'callback' => 'NewAddress_ajax_callback',
        'wrapper' => 'AddAddress_wrapper',
        'method' => 'replace',
      ),
      '#prefix' => '<div id="AddAddress_wrapper">',
      '#suffix' => '</div>',
      '#limit_validation_errors' => array(),
      '#submit' => array(),
    );
  }