In order to workaround this bug, you can handle the OnClientNodeClicking client-side event of the embeddedTree and cancel the propagation of the event if the node that is about to be selected is disabled:

 protected void Page_Load(object sender, EventArgs e)
 {
        Reporting.EmbeddedTree.OnClientNodeClicking = "OnClientNodeClicking";
 }

<script type="text/javascript">
            function OnClientNodeClicking(sender, args) {
                var nodeToSelect = args.get_node();

                if (!nodeToSelect.get_enabled())
                    args.set_cancel(true);
            }
        </script>

The DropDownTree pop-up is not positioned properly when the <form> is wrapped inside a relatively positioned element with fixed width.

The issue can be reproduced with a similar configuration:

    <div style="width: 700px; position: relative; left:300px">
        <form id="form1" runat="server">
            <telerik:RadScriptManager runat="server"></telerik:RadScriptManager>
            <div class="position">
                <telerik:RadDropDownTree runat="server" ID="ddt1" CssClass="dropDownTree"></telerik:RadDropDownTree>
            </div>
        </form>
    </div>

When I set the RadDropDownTree Enbaled as False, the Clear button still working and clear the Selected value.

Validation is not working as expected in Dropdowntree. In the demo page http://demos.telerik.com/aspnet-ajax/dropdowntree/examples/validation/defaultcs.aspx, if any one node is checked, the validation message "You need to select a type or a category before submitting the page" is displayed. If multiple checkboxes are checked, the message is not displayed. I do not want the validation message displayed when  check box is  checked.