object reference not set to instance of the object error in the xml filel

Hi all,
i am getting the above error while loading the data from the xml file 
here is the code that i wrote 

m_xmld = new XmlDocument();
// Load the Xml file
m_xmld.Load("C:\\Users\\bpucha1103c\\Desktop\\DNSNotifications1114.xml");
DNSNotifications_BL clsObj = new DNSNotifications_BL();
clsObj.setDNSXML_BL("Status", m_xmld.InnerXml.Trim());
XmlNamespaceManager nsMan = new XmlNamespaceManager(m_xmld.NameTable);
nsMan.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
nsMan.AddNamespace("noNamespaceSchemaLocation", "http://mecbh/DNSNotifications/dns_status_notification.xsd");
XmlNodeList dns_nodelist;
XmlNodeList dns_serlocnodelist;
XmlNodeList dns_devnodelist;
dns_nodelist = m_xmld.SelectNodes("/dns_status_notification", nsMan);
dns_serlocnodelist = m_xmld.SelectNodes("/dns_status_notification/service_locations/service_location", nsMan);
dns_d ...