ActiveX TreeView HRESULT E_FAIL

I am trying to use an ActiveX TreeView in SAP Business One form.

Even though I follow the example provided in the Business One SDK help, it doesn't work at all and I get a COM exception early in the code:

Item oItem = Form.Items.Add("xml", SAPbouiCOM.BoFormItemTypes.it_ACTIVE_X);
            oItem.Visible = true;
            oItem.Top = 5;
            oItem.Left = 5;
            oItem.Width = 290;
            oItem.Height = 490;

            ActiveX AcXTree = oItem.Specific;
            AcXTree.ClassID = "MSComctlLib.TreeCtrl.2"; 
            MSComctlLib.TreeView2 treeView = AcXTree.Object;//EXCEPTION

Exception:System.Runtime.InteropServices.COMException wurde nicht von Benutzercode behandelt.
  Message=Beim Aufruf einer COM-Komponente wurde ein HRESULT E_FAIL-Fehler zurückgegeben.
  Source=EGR_IQone
  ErrorCode=-2147467259
  StackTrace:
       bei SAPbouiCOM.IActiveX.get_Object()

I also tried using the ActiveX TreeView class guid {C74190B4-8589-11D1-B16A-00C0F0283628} but I get the same result.

I use Windows 7 64Bit and successfully registered MSComctl.ocx. I already asked on the SAP forum but did not get any answers so far.

And is there a way to tell what went wrong? Apparently E_FAIL is a general failure and it tells me nothing.

Thanks.