I have a static table in Radwindow's <ContentTemplate> tag. Upon popping up the Radwindow, it opens as collapsed for IE9. Works fine with rest of the major browsers, vis. IE 8, IE 9 Compat mode, FF, Chrome. 
Here is my code
Code behind:
protected void btnOpen_Click(object sender, EventArgs e)
{
TestDialog.VisibleOnPageLoad = true; // Pop up the radwindow
}
                                Here is my code
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>
<%@ Register TagPrefix="telerik" Namespace="Telerik.Web.UI" Assembly="Telerik.Web.UI" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <style type="text/css">
        .hide
        {
            overflow: hidden;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
    <div style="overflow: hidden;">
        <table cellspacing="0" border="0" style="table-layout: auto;">
            <tbody>
                <tr>
                    <th style="width: 100px;">
                        Column 1
                    </th>
                    <th style="width: 100px;">
                        Column 2
                    </th>
                </tr>
                <tr>
                    <td>
                        a
                    </td>
                    <td>
                        a
                    </td>
                </tr>
                <tr>
                    <td>
                        b
                    </td>
                    <td>
                        b
                    </td>
                </tr>
                <tr>
                    <td>
                        c
                    </td>
                    <td>
                        c
                    </td>
                </tr>
            </tbody>
        </table>
    </div>
    <br />
    <br />
    <br />
    <br />
    <telerik:RadScriptManager ID="scriptManager" runat="server" />
    <telerik:RadButton ID="btnOpen" runat="server" Text="Open" OnClick="btnOpen_Click" />
    <br />
    <telerik:RadWindow ID="TestDialog" runat="server" Title="Select Order Services" VisibleStatusbar="false"
        AutoSize="true" AutoSizeBehaviors="Height" Width="400px" Modal="true" VisibleOnPageLoad="false" Behaviors="Close, Move"
        EnableShadow="true" CssClass="hide">
        <ContentTemplate>
            <div>
                <table cellspacing="0" border="0" style="table-layout: auto;">
                    <tbody>
                        <tr>
                            <th style="width: 100px;">
                                Column 1
                            </th>
                            <th style="width: 100px;">
                                Column 2
                            </th>
                        </tr>
                        <tr>
                            <td>
                                a
                            </td>
                            <td>
                                a
                            </td>
                        </tr>
                        <tr>
                            <td>
                                b
                            </td>
                            <td>
                                b
                            </td>
                        </tr>
                        <tr>
                            <td>
                                c
                            </td>
                            <td>
                                c
                            </td>
                        </tr>
                    </tbody>
                </table>
            </div>
        </ContentTemplate>
    </telerik:RadWindow>
    </form>
</body>
</html>
protected void btnOpen_Click(object sender, EventArgs e)
{
TestDialog.VisibleOnPageLoad = true; // Pop up the radwindow
}