RadComboBox don't dropdown on Click in Text when in a RadWindow modal container

[Chris Wruck]

I have placed a RadComboBox inside a RadWindow I am using as a modal popup to capture some info. The RadComboBox is dynamically databound to a datatable result set and I can confirm that the data is loaded into the RadComboBox by clicking Up/Down arrows, I can see the other entries. However, clicking on the dropdown button, the dropbox will not expand. I have also tried the basic RadDropDownList with the same result.

I then tried an asp:DropDownList and it work's correctly. 

If I place the RadComboxBox outside of the RadWindow, it works. There are no javascript errors on the page.

 

Can anyone help?

<telerik:RadWindow ID="Results_popup" runat="server" Title="Import Results" VisibleTitlebar="true" VisibleStatusbar="false" VisibleOnPageLoad="false"
    Modal="true" Width="900px" height="600px" DestroyOnClose="True" KeepInScreenBounds="true" OnClientClose="ClosePopUpWindow_Replace"
    Behaviors="Close, Move, Resize">
    <ContentTemplate>
        <div id="inner-container" class="window-container">
            <asp:UpdatePanel ID="UpdatepanelListEdit" runat="server" UpdateMode="Conditional" RenderMode="Block" Visible="false">
                <ContentTemplate>
                        <div class="row">
                            <telerik:RadComboBox RenderMode="Lightweight" ID="drpListStatus" runat="server" Width="200" Label="Status:" />
                            <telerik:RadDropDownList ID="drpListStatusX" runat="server" />
                            <asp:DropDownList ID ="drpListStatusTmp" runat="server" CssClass="dropdown" />
                        </div>
                </ContentTemplate>
            </asp:UpdatePanel>
        </div>
    </ContentTemplate>
</telerik:RadWindow>

[Chris Wruck]

I found the answer which may help someone else.

 

I required  ZIndex="11000"