Removing of custom gwt widgets

For last several days I was trying to rewrite Toolbox addon.
So there is a problem that when I’m trying to remove the resulting component it disappears from the server but it remains on the client side.
The same situation appears when I put the Toolbox in a layout and after that replace the layout with another one without Toolbox.
Also the same problem is in the Ikarus addon.
Can anybody describe why is it so and how to fix it?