Hello, I tested in Lazarus 4.0RC, and I have not problem
procedure TForm1.FormCreate(Sender: TObject);
var
XmlDoc: TXMLDocument;
Root: TDOMElement;
begin
XmlDoc := TXMLDocument.Create;
Root := XmlDoc.CreateElement('catalogocuentas:Catalogo');
Root.AttribStrings['aa']:='ggg';
Which Lazarus did use? and Operating System?
/BlueIcaro