SkinFramework not applied to all Controls on Form

I took the SkinMDISample as a template project to develop an application that features an MDI-Interface, a Ribbon-Bar (XtremeCommandBars) and a Docking-Pane Interface (XtremeDockingPane). My intention was to apply a skin on all the controls/forms. I had to keep in mind the following points:

1) The Ribbon-Bar object (of type AxCommandBars), the Docking-Pane object (AxDockingPane) and the skin-framework object (AxSkinFramework) are on the main-form.

2) The main-form is the MDI-parent

3) The MdiParent-property is set on every child-form to the main-form

4) The Ribbon-bar uses another technique to apply skins. Therefore the ApplyWindow() method must not be applied for the main-form

5) The ApplyWindow() method is applied for each child-form (this is done in the OnVisibleChanged()-method)

6) OnBackColorChanged() is called for every child-form

 

The skin is properly applied for the Ribbon-bar as well as for most other controls. BUT: There are some controls that do not apply the skin (e.g. DataGridView, or some scroll-bars). I don't know what might be wrong, because in my opinion, it's the same logic as in the sample application.