blank screen using desktop example

[sony1464]

I am trying to use the desktop sample using version 1.0. I am using user control in my code. When the page loads I see a blank screen on the desktop., I also tried another sample with a tree control within a user control and it renders on the desktop when it loads.whats the reason behind this ??

---aspx page
-----------

<ext:Desktop ID="MyDesktop" runat="server" BackgroundColor="Black" ShortcutTextColor="White"
Wallpaper="desktop.jpg">
<Modules>

<ext:DesktopModule ModuleID="DesktopModule4" WindowID="winFeedback">
<Launcher ID="Launcher4" runat="server" Text="Permissions" Icon="World" />
</ext:DesktopModule>

</Modules>
<Shortcuts>

<ext:DesktopShortcut ModuleID="DesktopModule4" Text="Feedback" IconCls="shortcut-icon icon-window48" />

</Shortcuts>
</ext:Desktop>

<ext:DesktopWindow ID="winFeedback" runat="server" Title="Feedback" Icon="World"
Width="610" Height="450" PageX="25" PageY="25" Layout="Fit">
<Content>
<uc7:Feedback runat="server" ID="Feedback1" />
</Content>
</ext:DesktopWindow>

---------------------------
user control
----------------------

<ext:Panel ID="Panel5" runat="server" Title="Inner Tabs" Width="600" Padding="5"
ButtonAlign="Center" Header="false" AutoScroll="true" >
<Items>
<ext:Container ID="Container1" runat="server" Layout="Column" Height="200">
<Items>
<ext:Container ID="Container2" runat="server" LabelAlign="Top" Layout="Form" ColumnWidth=".5">
<Items>
<ext:ComboBox ID="cbType" runat="server" FieldLabel="Feedback Type" AnchorHorizontal="95%" />
<ext:ComboBox ID="ComboBox2" runat="server" FieldLabel="Project" AnchorHorizontal="95%" />
</Items>
</ext:Container>
<ext:Container ID="Container3" runat="server" LabelAlign="Top" Layout="Form" ColumnWidth=".5">
<Items>
<ext:FileUploadField ID="ComboBox1" runat="server" FieldLabel="Attachment" AnchorHorizontal="95%" />
<ext:HtmlEditor ID="HtmlEditor1" runat="server" />
</Items>
</ext:Container>
</Items>
</ext:Container>

</Items>
<Buttons>
<ext:Button ID="Button1" runat="server" Text="Save" />
<ext:Button ID="Button2" runat="server" Text="Cancel" />
</Buttons>
</ext:Panel>