[Solved] Exception on Export after implementing custom filter

[Darwin]

I recently created a custom drop down filter for use in a RadGrid.  I followed the example from these two links:
http://demos.telerik.com/aspnet-ajax/grid/examples/programming/filteringtemplatecolumns/defaultcs.aspx
http://www.telerik.com/help/aspnet/grid/grdfilteringwithdropdownlist.html

The grid shows a list of sites.  The drop down displays a list of statuses that can pertain to requests belonging to the site.  See attached screen shot. The column displays a count showing how many of that site's requests have the selected status. 

The grid has an ExportToExcel button.  When clicking that button, the custom control throws the following exception:
 

2013-04-26 10:01:37.923,0000000F,OPSWeb,Unhandled Application Exception [Page Info: /OPSWeb/OPSMain.aspx],Error,Unable to cast object of type 'Telerik.Web.UI.CompressedPageState' to type 'System.Collections.IDictionary'.

10:21

The error occurs in this method on the last line where it adds the combox to the list of controls in the cell..  

        protected override void SetupFilterControls(TableCell cell)
        {
            rcBox = new RadComboBox();
            rcBox.ID = ID;
            rcBox.AutoPostBack = true;
            rcBox.Width = FilterControlWidth;
            rcBox.SelectedIndexChanged += rcBox_SelectedIndexChanged;
            rcBox.DataSource = StatusList;
            cell.Controls.Add(rcBox);
        }

How do I get the export to work?  Why is this causing the export to fail?

Thank you.

[Kostadin]

Hello Darwin,

I was not able to replicate the issue on my side. I prepared a a small sample where I used the example which you used to create your project. As you could see everything work properly. It would be best if you could replicate the issue in a small runnable sample in order to investigate the issue further.

Greetings,
Kostadin
the Telerik team