I'm using 2 Docking Managers, 1 for my main form and the second for a UserControl which acts as a container for other user controls. The docking state saves and restores correctly when the docking state for controls within the main form changes.
But as soon as the docking state changes on the controls within the User Control container the LoadDockState method fails.
I've attached a very simple test app.
To recreate the problem just move the splitter bar between "Test Panel 3" and "Test Panel 4" and and then click the "Restore Layout" menu option
Docking Manager.zip