There could be different reasons for this to take place. On moving the dock to another zone does a postback take place (have you set RadDock's property autopostback=true)? Are you re-adding the dock's content every time because if you are adding the content on !IsPostBack then on the next postback the content will be lost.
I am going to ask you once again to send us your code as it is not possible to predict what could be happening without seeing the whole picture. You see that without code it takes us a couple of posts to discuss a simple matter and helping you takes much longer than it would if we could see the code. I kindly ask you to provide us with a simple running project and tell us what you try to achieve and we will provide accurate assistance as soon as possible.
the Telerik team