Hello Miroslav Nedyalkov
another member of telerik team has already answered at my question, but I can't replay to his post because telerik's forum says that there is a server error, so I ask you if you know how to resolve my problem.
(old topic: http://www.telerik.com/community/forums/silverlight/general-discussions/radpanegroup-lost-the-style.aspx
I have to style the docking, unfortunately I'm not be able to style the toolwindow and the Document1 (in the project).
Here is the entire solution
, please check it out as soon as possible :)