Sqlxml

[HaJe]

Hi!
This is what I'm trying to do:
Query my SQL server with sqlxmladapter and populate a datagrid with the resulting dataset, make changes to the dataset and update the database.
All works fine until i try to update fields in a table under/below the top-node. This is the exception I get:
"SqlXmlException: <?MSSQLError HResult="0x80040e14" Source=Microsoft OLE DB Provider for SQL Server" Description="SQLOLEDB Error Description: Empty update, no updatable rows found Transaction aborted"?>
Its a bit tricky to explain and I will paste some code to make it easier to understand.

// Use this to populate dataset and grid
private void button1_Click(object sender, System.EventArgs e)
		{
			cmd = new SqlXmlCommand("Provider=SQLOLEDB;"+sqlConnection1.ConnectionString);
			cmd.RootTag = "ROOT";
			cmd.CommandText = "tbl_Arende";

			cmd.CommandType = SqlXmlCommandType.XPath;
			cmd.SchemaPath = @"..\..\Schema1.xsd";

			ad = new SqlXmlAdapter(cmd);
			
			ds = new DataSet();			
			ad.Fill(ds);

			dataGrid1.DataSource = ds;
			ds.WriteXml(@"..\..\Output.xml");
		}

// Use this to update changes made in the grid
private void button2_Click(object sender, System.EventArgs e)
		{
			if(ds.HasChanges())
			{
				ds.GetChanges().WriteXml(@"..\..\Diffgram.xml" ,XmlWriteMode.DiffGram);
				string err = "";
				try
				{
					ad.Update(ds.GetChanges());
					ds.AcceptChanges();
				}
				catch (SqlXmlException ex)
				{
					ex.ErrorStream.Position = 0; 
					StreamReader errreader = new StreamReader(ex.ErrorStream); 
					err = errreader.ReadToEnd();
					errreader.Close();
					MessageBox.Show("SqlXmlException: " + err);
					ds.AcceptChanges();
				}	
			}
		}

And here is the Schema1.xsd I've made

<?xml version="1.0" encoding="utf-8" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:sql="urn:schemas-microsoft-com:mapping-schema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
	<xsd:annotation>
		<xsd:appinfo>
			<sql:relationship name="FK_tbl_Handelse_tbl_Arende" parent="tbl_Arende" parent-key="PkID" child="tbl_Handelse" child-key="Fk_Arende" />
			<sql:relationship name="FK_tbl_ArendeData_tbl_Arende" parent="tbl_Arende" parent-key="PkID" child="tbl_ArendeData" child-key="Fk_Arende" />
			<sql:relationship name="FK_tbl_HandelseData_tbl_Handelse" parent="tbl_Handelse" parent-key="PkID" child="tbl_HandelseData" child-key="Fk_Handelse" />
		</xsd:appinfo>
	</xsd:annotation>
	<xsd:element name="tbl_Arende">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element name="tbl_ArendeData" sql:relationship="FK_tbl_ArendeData_tbl_Arende">
					<xsd:complexType>
						<xsd:attribute name="PkID" type="xsd:int" sql:identity="ignore" />
						<xsd:attribute name="myField" type="xsd:string" />
						<xsd:attribute name="myValue" type="xsd:string" />
					</xsd:complexType>
				</xsd:element>
				<xsd:element name="tbl_Handelse" sql:relationship="FK_tbl_Handelse_tbl_Arende">
					<xsd:complexType>
						<xsd:sequence>
							<xsd:element name="tbl_HandelseData" sql:relationship="FK_tbl_HandelseData_tbl_Handelse">
								<xsd:complexType>
									<xsd:attribute name="PkID" type="xsd:int" sql:identity="ignore" />
									<xsd:attribute name="myField" type="xsd:string" />
									<xsd:attribute name="myValue" type="xsd:string" />
								</xsd:complexType>
							</xsd:element>
						</xsd:sequence>
						<xsd:attribute name="PkID" type="xsd:int" sql:identity="ignore" />
					</xsd:complexType>
				</xsd:element>
			</xsd:sequence>
			<xsd:attribute name="PkID" type="xsd:int" sql:identity="ignore" />
			<xsd:attribute name="DiarieNummer" type="xsd:string" />
		</xsd:complexType>
	</xsd:element>
</xsd:schema>

And here's an example of a diffgram due to changes made:

<?xml version="1.0" standalone="yes"?>
<diffgr:diffgram xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1">
  <ROOT>
    <tbl_Arende diffgr:id="tbl_Arende1" msdata:rowOrder="0" msdata:hiddentbl_Arende_Id="0" PkID="1" DiarieNummer="1234567">
      <tbl_ArendeData diffgr:id="tbl_ArendeData1" msdata:rowOrder="0" diffgr:hasChanges="modified" myValue="RemissChanged" PkID="1" myField="ArendeTyp" msdata:hiddentbl_Arende_Id="0" />
    </tbl_Arende>
  </ROOT>
  <diffgr:before>
    <tbl_ArendeData diffgr:id="tbl_ArendeData1" msdata:rowOrder="0" myValue="Remiss" PkID="1" myField="ArendeTyp" msdata:hiddentbl_Arende_Id="0" />
  </diffgr:before>
</diffgr:diffgram>

If I make changes to tbl_Arende which is the top node, update works fine, but if I make changes in any underlaying related tables I get the exception I described.
All the relations in the DB are correct and corresponds to the ones in the Schema1.xsd.

Thankful for any ideas or suggestions.
// HaJe