I test starting from VS2005 out of C # on a simple list of contact with 1 only column. Here my code:
WebReference1.Lists listService = new WebReference1.Lists();
listService.Credentials = System.Net.CredentialCache.DefaultCredentials;
string strBatch = "<Method ID='1' Cmd='Update'>" +
"<Field Name='Title'>TestTestTest</Field></Method>";
XmlDocument xmlDoc = new System.Xml.XmlDocument();
System.Xml.XmlElement elBatch = xmlDoc.CreateElement("Batch");
elBatch.SetAttribute("OnError", "Continue");
elBatch.SetAttribute("ListVersion", "1");
elBatch.SetAttribute("Contacts", "128AF617-5070-4183-A9ED-D54FB171B9DA");
elBatch.InnerXml = strBatch;
XmlNode ndReturn = listService.UpdateListItems("Contacts", elBatch);
MessageBox.Show(ndReturn.OuterXml);
I obtain an error indicating to me that the URL is not correct...
My URL of Webreference :
http://10.20.20.103:88/_vti_bin/Lists.asmx
and URL of list :

:( HELP please.