If you want to preserve the RadDock state after a Postback you should wrap all RadDockZones and RadDocks with RadDockLayout.
Here are several examples which illustrates how to save/load RadDock state
1) SaveState in cookies
2) Dynamically created RadDocks and save their state in session
You should load the state in RadDockLayout.LoadDockLayout event handler and save it in RadDockLayout.SaveDockLayout event handler.
the Telerik team