CPropertySheet/CTabCtrl GetItem(...) with TCIF_PARAM = errors

Hi,

I have a fairly straightforward subclassed CProperpySheet and I am doing
some small work with the TabControl.

So in my Inidialog I subclass the tab control.

BOOL CMySheet::OnInitDialog()
{
  BOOL bResult = CPropertySheet::OnInitDialog();

  m_tabCtrl.SubclassDlgItem(
CPropertySheet::GetTabControl()->GetDlgCtrlID(), this );

  return bResult;
}

Then in my tab control, when the user clicks on a tab I do...

{
....
  TCHAR sSrcBuffer[256] = {0};
  TCITEM tcitem;
  tcitem.mask = TCIF_IMAGE | TCIF_TEXT | TCIF_PARAM | TCIF_STATE;
  tcitem.pszText = sSrcBuffer;
  tcitem.cchTextMax = _countof(sSrcBuffer);
  BOOL bOK = GetItem(nSrcTab,&tcitem);
  assert(bOK);
....
}

I do nothing to the control before and after.
I then get an error when I exit the function, (in the destructor of the
local variables).

"Run- Time check failure #2 - Stack around the variable 'xxx' was corrupted"

When I change the Mask to

tcitem.mask = TCIF_IMAGE | TCIF_TEXT | TCIF_STATE;

Everything works fine

What could be the problem? I am using VS2008.

Many thanks

Simon