I am using a WebDialogWindow to allow the user to input data to my application.

I'm having a problem when I add a RequiredFieldValidator control to the ContentPane - when I do, the WebDialogWindow no longer displays.

The WDW is in an UpdatePanel, and works fine (here is an example of my WDW)

This behavior is the same in FireFox and IE7.

Working WDW:

<cc1:WebDialogWindow ID="MyDialog" runat="server" Height="300px"

    Width="400px" WindowState="Hidden" InitialLocation="Centered" Modal="True"

        Moveable="False" CssClass="dialogForm" >

    <Header CaptionText="Add a Device" />

    <ContentPane>

        <Template>

            <div >

            <br />

            <asp:Label ID="Label1" runat="server" Text="IP Address:"></asp:Label>

            <asp:TextBox ID="IP_Addr_TextBox" runat="server"></asp:TextBox>

            <br />

            <asp:Label ID="Label2" runat="server" Text="Name:"></asp:Label>

            <asp:TextBox ID="Name_TextBox" runat="server"></asp:TextBox>

            <br />

            <asp:Label ID="Label3" runat="server" Text="Model:"></asp:Label>

            <asp:DropDownList ID="Model_DropDownList" runat="server">

            </asp:DropDownList>

            <br />

            <asp:Button ID="ButtonOK" runat="server" Text="OK" onclick="ButtonOK_Click" />

            <asp:Button ID="ButtonCancel" runat="server" C***alidation="False"

                    Text="Cancel" oncommand="ButtonCancel_Command" />

            </div>

        </Template>

    </ContentPane>

</cc1:WebDialogWindow>

By simply adding a

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"

                                ErrorMessage="RequiredFieldValidator" ControlToValidate="IP_Addr_TextBox" />

makes not only this WebDialogWindow fail to display, but also affects my other WDW onthis page -

What is causing this? Any ideas? I really want to use asp:RequiredFieldValidator on my dialog.