protected override void OnAfterLabelEdit(NodeLabelEditEventArgs e)
{
    base.OnAfterLabelEdit(e);

    TreeNode node = e.Node;

    if (PassesSomeValidation(e.Label))
    {
        MyDataNode dataNode = node.Tag as MyDataNode;
        dataNode.SomeBoundValue = e.Label;

        int oldIndex = node.Index;
        int newIndex = RepositionChangedDataNode(dataNode);

        TreeNode parent = node.Parent;
        parent.Nodes.RemoveAt(oldIndex);
        parent.Nodes.Insert(newIndex, node);
    }
    else
    {
        e.CancelEdit = true;
    }
}

BeginInvoke(new MethodInvoker(delegate(
{
    parent.Nodes.RemoveAt(oldIndex);
    parent.Nodes.Insert(newIndex, node);
}));

private bool _allowEdit;

... int oldIndex = node.Index;
    int newIndex = RepositionChangedDataNode(dataNode);

    TreeNode parent = node.Parent;
    parent.Nodes.RemoveAt(oldIndex);
    parent.Nodes.Insert(newIndex, node);
    **_allowEdit = false;**
}
else ...

protected override void OnBeforeLabelEdit(NodeLabelEditEventArgs e)
    {
        base.OnBeforeLabelEdit(e);
        e.CancelEdit = !_allowEdit;
        _allowEdit = true;
    }