UpdatePanelAnimationExtender and nested UpdatePanel

[Clodoaldo]

I'm trying to make animations work with nested UpdatePanels.

The outermost UpdatePanel is correctly FadedOut and FadedIn but the
inner UpdatePanel is only FadedOut, it is not FadedIn OnUpdated:

<div>

<asp:UpdatePanel ID="UpdatePanel1" runat="server"
UpdateMode="conditional">
<ContentTemplate>
<aspropDownList ID="DropDownList1" runat="server"
AutoPostBack="true"
OnSelectedIndexChanged="DropDownList_SelectedIndexChanged">
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
</aspropDownList>

<asp:UpdatePanel ID="UpdatePanel2" runat="server"
UpdateMode="conditional">
<ContentTemplate>
<aspropDownList ID="DropDownList2" runat="server"
AutoPostBack="true"

OnSelectedIndexChanged="DropDownList_SelectedIndexChanged">
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
</aspropDownList>
</ContentTemplate>
</asp:UpdatePanel>

</ContentTemplate>
</asp:UpdatePanel>

<ajaxToolkit:UpdatePanelAnimationExtender
ID="UpdatePanelAnimationExtender1"
TargetControlID="UpdatePanel1" runat="server">
<Animations>
<OnUpdating><FadeOut duration="0.2" fps="20"
minimumOpacity="0.35"></FadeOut></OnUpdating>
<OnUpdated><FadeIn duration="0.2" fps="20"></FadeIn></OnUpdated>
</Animations>
</ajaxToolkit:UpdatePanelAnimationExtender>

</div>
</form>


protected void DropDownList_SelectedIndexChanged(object sender,
EventArgs e)
{
System.Threading.Thread.Sleep(1000);
}


What am I missing?

Regards, Clodoaldo Pinto Neto