In order for the master-details to work, both grid''s need to be using the same binding context. Normally, the grid takes its binding context from its parent.
Try handling the DockedStateChanged event and force the two grids to have teh same BindingContext.
private void dockingManager1_DockStateChanged(object sender, DockStateChangeEventArgs arg)
{
if(this.gridDataBoundGrid1.BindingContext == null)
this.gridDataBoundGrid1.BindingContext = new BindingContext();
this.gridDataBoundGrid2.BindingContext = this.gridDataBoundGrid1.BindingContext;
}