Icon missing when adding custom combobox command to Toolbar

[Andreas_W_Paulsen]

I have a custom command:

class ATL_NO_VTABLE CSliceSelector :
 public CComObjectRootEx<CComSingleThreadModel>,
 public CComCoClass<CSliceSelector, &CLSID_SliceSelector>,
 public ISliceSelector,
 public ICommand,
 public IComboBox
{
   ...
}

I also have a custom Toolbar where I try to add my custom command:

class ATL_NO_VTABLE CSeismicToolbar :
 public CComObjectRootEx<CComSingleThreadModel>,
 public CComCoClass<CSeismicToolbar, &CLSID_SeismicToolbar>,
 public ISeismicToolbar,
 public IToolBarDef
{
   ...
   STDMETHOD(GetItemInfo)(long pos, IItemDef * itemDef) {
  if (itemDef == NULL)
   return E_POINTER;

  if (pos == 0) { // CSliceSelector 
   itemDef->put_Group (VARIANT_FALSE);
   HRESULT hr = itemDef->put_ID(CComBSTR(L"{96A2B223-BF0D-410C-B22B-892FED3D9A15}"));
   if (FAILED (hr)) {
    return hr;
   }
  } 
      }
}

However when I start ArcScene; I see a red circle icon and the text "Missing" (see the attached image), instead of my command :-(.

However if I add it manually from Customize toolbars; it works fine.

I have tried both returning a null pointer and a valid bitmap:

CSliceSelector()
{
     m_hBitmap = ::LoadBitmap(_AtlBaseModule.GetModuleInstance(),MAKEINTRESOURCE(IDB_SLICE));
}
STDMETHODIMP CSliceSelector::get_Bitmap(OLE_HANDLE * Bitmap)
{
     if (Bitmap == NULL)
        return E_POINTER;
   *Bitmap = (OLE_HANDLE) m_hBitmap;
     return S_OK;
}

I have other commands that are not combobox; and they work fine.