Can anybody tell me why navigating xml with an instruction fails :

```
StringBuilder   sb2 = new System.Text.StringBuilder();
XmlDocument     doc = new XmlDocument( );

// --- XML without instruction -> Parsing succeeds 
sb1.AppendLine( @"<MetalQuote>");
sb1.AppendLine( @"<Outcome>Success</Outcome>");
sb1.AppendLine( @"<Ask>1073.3</Ask>");
sb1.AppendLine( @"</MetalQuote>");

doc.LoadXml( sb1.ToString( ));
System.Diagnostics.Debug.WriteLine( doc.SelectSingleNode( "//MetalQuote/Outcome").InnerText);

```

This works well, but the same XML with an instruction fails :

```
// --- XML with instruction -> Parsing fails 
sb2.AppendLine( @"<MetalQuote xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"" xmlns:xsd=""http://www.w3.org/2001/XMLSchema"" xmlns=""http://www.xignite.com/services"" >");
sb2.AppendLine( @"<Outcome>Success</Outcome>");
sb2.AppendLine( @"<Ask>1073.3</Ask>");
sb2.AppendLine( @"</MetalQuote>");

doc.LoadXml( sb2.ToString( ));
System.Diagnostics.Debug.WriteLine( doc.SelectSingleNode( "//MetalQuote/Outcome").InnerText);

```

I get an exception at the doc.SelectSingleNode statement.