Telerik RadComboBox: Everytime Check-All is selected I get the JavaScript error: A script on this page is causing your web browser to run slowly

Question

I have a RadComboBox that has around 400 items (from a DataBase) and I get the following JavaScript error as soon as I select "Check All":

A script on this page is causing your web browser to run slowly. If it continues to run, your computer might become unresponsive.

To optimize the CombBox I have set LoadOnDemand to true & OnClientItemsRequesting="StopRequest", but this does not seem to help.

ComboBox Properties aspx code:

        <telerik:RadComboBox ID="CUD" 
            Width="260" 
            Height="150" 
            runat="server" 
            AutoPostBack="false" 
            CheckBoxes="true"
            EnableCheckAllItemsCheckBox="true">

            </telerik:RadComboBox>

Answer 1

It's the TelerikRadComboBox, I created a test project and tested with just the DropDown and 400 ListItems (and clicked CheckAll) and got the same error. There was no JavaScript executed that was personally written. An Admin responded saying thank you for reporting the error, your implementation is accurate I will forward the issue to the Development team for performance improvements... In general IE8 is slower than the others like some of you have mentioned which is why the error is caused solely on IE8.