Button texts disappears after changing to Theme Windows XP

Hi,
  I have a simple dialog just for inputting text. This dialog has a
input field, and OK Cancel button.
In windows classic theme, everything is OK, but if the windows theme
is changed to Windows XP, the texts on OK and Cancel buttons just
disappear. The dialog's title is still there, BTW.
What could be the reason?
Thanks.

To help your analysis, I give my codes here:

#include "WhiteboardTextEntryDialog.h"
#include "ComponentsID.h"
#include "Data/ResourcesManager.h"

BEGIN_MESSAGE_MAP(WhiteboardTextEntryDialog, SkinDialog)
    ON_BN_CLICKED( IDOK, onOKButtonClicked )
    ON_BN_CLICKED( IDCANCEL, onCancelButtonClicked )
    ON_WM_CREATE()
    ON_WM_DESTROY()
END_MESSAGE_MAP()

WhiteboardTextEntryDialog::WhiteboardTextEntryDialog( CWnd*
parent ) :
    SkinDialog( whiteboardTextInputDlg )
{
    SMCENTRY( "" );
    create( parent );
    // We set the OK button the default one
    PostMessage( DM_SETDEFID, okButton_.GetDlgCtrlID() );

    // Position the window.
    POINT pos;
    GetCursorPos( &pos );
    SetWindowPos( NULL, pos.x, pos.y, 200, 90, SWP_SHOWWINDOW );

    // We have to set the text here because someone resets it right
after OnCreate()
    Data::ResourcesManager& resMan =
Data::ResourcesManager::instance();

SetWindowText( resMan.getString(L"WHITEBOARD_TEXTINPUT_TITLE").c_str() );

}

void WhiteboardTextEntryDialog::onOKButtonClicked()
{
    SMCENTRY( "" );
    CString str;
    textField_.GetWindowText( str );
    text_ = str;
    endDialog( IDOK );

}

void WhiteboardTextEntryDialog::onCancelButtonClicked()
{
    SMCENTRY( "" );
    endDialog( IDCANCEL );

}

void WhiteboardTextEntryDialog::OnDestroy()
{
    SMCENTRY( "" );
    endDialog( IDCANCEL );

}

int WhiteboardTextEntryDialog::OnCreate(LPCREATESTRUCT
lpCreateStruct)
{
    SMCENTRY( "" );
    if (SkinDialog::OnCreate(lpCreateStruct) == -1)
    {
        return -1;
    }

    Data::ResourcesManager& resMan =
Data::ResourcesManager::instance();

    //Try to set the font.
    CFont f;
    f.CreateStockObject(DEFAULT_GUI_FONT);
    SetFont(&f);

    LOGFONT lf;
    f.GetLogFont(&lf);

    CRect rect( 4, 4, 190, 24 );
    textField_.Create( WS_CHILD | WS_BORDER | WS_VISIBLE | WS_TABSTOP
| WS_GROUP | ES_AUTOHSCROLL,
        rect, this, whiteboardTextInputField );
    textField_.SetFocus();
    textField_.SetLimitText( 50 );
    textField_.SetFont(&f);

    rect.SetRect( 4, 30, 64, 50 );
    okButton_.Create( resMan.getString(L"OK").c_str(),
        WS_CHILD | WS_VISIBLE | WS_TABSTOP | BS_DEFPUSHBUTTON, rect,
this, IDOK );

    okButton_.SetFont(&f);

    rect.SetRect( 70, 30, 130, 50 );
    cancelButton_.Create( resMan.getString(L"CANCEL").c_str(),
        WS_CHILD | WS_TABSTOP | WS_VISIBLE, rect, this, IDCANCEL );
    cancelButton_.SetFont(&f);

    //Return true because we set the default button.
    return TRUE;
}

============
The dialog is shown in a special way, as below. But I don't think it
has anything to do with this bug.

void WhiteboardSketchArea::textRequest()
{
    SMCENTRY( "" );
    WhiteboardTextEntryDialog dlg( this->GetTopLevelParent() );
    int result = ViewManager::instance().runModal( &dlg,
controller_ );
    if ( result == -1 )
        return; // Stack unwindinding due to abort
    if ( !dlg.text_.empty() )
    {
        CDC* dc = GetDC();
        CFont* oldFont = dc->SelectObject( &font_ );
        CSize size = dc->GetOutputTextExtent( dlg.text_.c_str() );
        dc->SelectObject( oldFont );
        ReleaseDC( dc );
        controller_->setText( dlg.text_, size.cx, size.cy );
    }