даже еще проще:

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop
#include "uidn.h"

//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TfmIdent *fmIdent;
//---------------------------------------------------------------------------
__fastcall TfmIdent::TfmIdent(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TfmIdent::loadOpt()
{
 short Ok;
 char* P1 = "x";
 IXMLDOMDocument* xOpt;

 CoCreateInstance (CLSID_DOMDocument, NULL,
   CLSCTX_INPROC_SERVER, IID_IXMLDOMDocument, (void**) &xOpt);

 VARIANT v;
 v.vt = VT_BSTR;
 v.bstrVal = L"x.xml";
 xOpt->load(v, &Ok);
 xOpt->Release();

}
//---------------------------------------------------------------------------
void __fastcall TfmIdent::FormShow(TObject *Sender)
{
 loadOpt();
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------

#ifndef uidnH
#define uidnH
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <Forms.hpp>
#include <msxml.h>

//---------------------------------------------------------------------------
class TfmIdent : public TForm
{
__published:    // IDE-managed Components
  void __fastcall FormShow(TObject *Sender);
private:
        void __fastcall loadOpt();
public:
        __fastcall TfmIdent(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TfmIdent *fmIdent;
//---------------------------------------------------------------------------
#endif

как я понял, глючит из-за

char* P1 = "x";

, причем если длина строки четная, то все OK