Mour,
The order has been already deleted from system in table sales_flat_order
.You need to check here.
I guess that order is in sales_flat_order_grid
database table but it doesn't exits on sale_flat_order
table which is main table of sales order
model[Mage::getModel('sales/order')
]
see at class Mage_Adminhtml_Sales_OrderController
where magento is check order is exit or not.
on function initorder
protected function _initOrder()
{
$id = $this->getRequest()->getParam('order_id');
$order = Mage::getModel('sales/order')->load($id);
if (!$order->getId()) {
$this->_getSession()->addError($this->__('This order no longer exists.'));
$this->_redirect('*/*/');
$this->setFlag('', self::FLAG_NO_DISPATCH, true);
return false;
}
Mage::register('sales_order', $order);
Mage::register('current_order', $order);
return $order;
}
That means order does not delete properly.
You need to delete those order from sales_flat_order_grid.