Updatepanel does not execute complete code

Hi,

I am using an updatepanel together with a UpdateProgress and ModalPopupExtender to show a "Loading" page when a button is click to synchronize with the server. The primary goal is to avoid that visitors can click twice during the execution of the code. As there are more buttons on the page, I use ModalPopupExtender to show a page-wide overlay.

Before I used this updatepanel the code behind worked fine. But since the updatepanel was added it seems that the codebehind is not completely executed. Do I miss someobvious?

<asp:UpdateProgress runat="server" ID="upLoading" DisplayAfter="0" DynamicLayout="true"><ProgressTemplate><div class="LoadingPopUpBackground"><div class="LoadingPopUp"><asp:Image ID="imgLoading" runat="server" AlternateText="Loading" ImageUrl="~/images/loader.gif" ToolTip="Loading" /><br /><asp:Label ID="lblLoadingMessage" runat="server" Text="Loading . . ." CssClass="LoadingText" /></div></div></ProgressTemplate></asp:UpdateProgress><ajaxToolkit:ModalPopupExtender ID="modularProcessing" runat="server" TargetControlID="upLoading" PopupControlID="upLoading" DropShadow="false" /><asp:UpdatePanel ID="upForwarding" runat="server"><ContentTemplate><asp:Button ID="btnForwarding" runat="server" Text="Forward" /><&nbsp;&nbsp;&nbsp;<asp:Button ID="btnForwardingCancel" runat="server" Text="Cancel" /></ContentTemplate></asp:UpdatePanel>

Thanks!