What I ment was, when I grab and pull out a RadPane from the PaneGroup, it then creates a CustomToolWindow, which is invisible.
In fact I am using the NoXaml Binaries. Changing to the normal Binaries does slightly change the visual appearance of the hole Application, that's why I have chosen your second suggestion, which worked as expected, with no visual sideeffects. Thank you.
So far I haven't really been thinking about the difference between those binaries, because both seem to work with Theming I have been randomly picking the NoXaml Bins, without asking no question during the Trial Phase, which I didn't change. Might you Post some links, which do exactly describe the different behavior upon styling, native look, and other characteristics in which they differ.
Thank you so far.