How to handle Forms Authentication Ticket Expiration with EnableLoadOnDemand

[B]

I've got a multi-column radComboBox that is working great except for 1 issue: 

The web app uses forms authentication...and when the cookie authentication ticket expires and the user types something into the radcombobox nothing happens...no error is returned/displayed and the web page is not redirected to the login.aspx page (which is what normally happens). 

A couple other things to note:

1. I've enabled EnableLoadOnDemand implementing OnItemsRequested at the page level.  When the user types into the radComboBox after the Auth Ticket has expired, I confirmed that Fiddler shows login.aspx being returned as the result...but radComboBox just shows "Loading..." and nothing happens.
2. I'm using latest version - Q2 2010

My Question:

How do i catch this scenario and is there a recommended best practice on how to handle it?  Preferably I would like to just have the radComboBox redirect to the Login.aspx page versus eating the page and just showing "Loading....".  Currently as it is, the user has to force a postback to get the page to redirect to login.aspx. 

Any suggestions much appreciated.  Sample code below:

<telerik:RadComboBox ID="RadComboBox1" runat="server" MarkFirstMatch="True" HighlightTemplatedItems="true"
                            EnableLoadOnDemand="true" ShowMoreResultsBox="true" Width="200px" Skin="Default"
                            DropDownWidth="350px" OnItemsRequested="RadComboBox1_ItemsRequested" DataTextField="FullName"
                            DataValueField="DirID" OnClientItemsRequestFailed="OnClientItemsRequestFailedHandler">
                            <HeaderTemplate>
                                <ul>
                                    <li class="col1">File ID</li>
                                    <li class="col2">Client Name</li>
                                    <li class="col3">Birth Date</li>
                                </ul>
                            </HeaderTemplate>
                            <ItemTemplate>
                                <ul>
                                    <li class="col1">
                                        <%# DataBinder.Eval(Container.DataItem, "DirID") %></li>
                                    <li class="col2">
                                        <%# DataBinder.Eval(Container.DataItem, "FullName") %></li>
                                    <li class="col3">
                                        <%# DataBinder.Eval(Container.DataItem, "Birthdate", "{0:d}") %></li>
                                </ul>
                            </ItemTemplate>
                        </telerik:RadComboBox>

[Simon]

Hello B,

Unfortunately this is an issue in the ASP.NET AJAX Framework. Fortunately we have a way to work around it as shown in this KB article.

I hope this helps.

Best wishes,
Simon
the Telerik team