Microsoft JScript Runtime error on SelectedIndexChanged event of RadComboBox

[Anup]

I have a RadComboBox with AutoPostBack property set to "True". When the SelectedIndexChanged of RadComboBox gets fired, the page does gets loaded completely, but suddenly after that it throws a javascript runtime error. The same happens even on click of a button too.

I have attached the snapshot of the error that pops up.

Even if i comment out all the code written in SelectedIndexChanged Event, still its throws the same javascript runtime error. So i think there is something wrong with the markup written (but not sure).

It would be of great help to me if you shed some light on the possibilities of what might be the cause of the error.

Please do reply on urgent basis, as i am stuck in my project due to this issue.

Thanks in advance.

<telerik:RadAjaxManager ID="radAjaxManager" runat="server" EnableHistory="True">
        <AjaxSettings>
           <telerik:AjaxSetting AjaxControlID="btnAddMembers">
             <UpdatedControls>
                    <telerik:AjaxUpdatedControl ControlID="radGvViewMembers" LoadingPanelID="radMembersLoadingPanel" />
                    <telerik:AjaxUpdatedControl ControlID="radGvViewExisitngMembers" LoadingPanelID="radMembersLoadingPanel" />
                    <telerik:AjaxUpdatedControl ControlID="lblImport"/>
                    <telerik:AjaxUpdatedControl ControlID="lblErrorImport"/>
                    <telerik:AjaxUpdatedControl ControlID="radComboDatabase"/>
                </UpdatedControls>
            </telerik:AjaxSetting>
        </AjaxSettings>
        <AjaxSettings>
            <telerik:AjaxSetting AjaxControlID="btnRemoveMembers">
                <UpdatedControls>
                    <telerik:AjaxUpdatedControl ControlID="radGvMembers" LoadingPanelID="radMembersLoadingPanel" />
                </UpdatedControls>
            </telerik:AjaxSetting>
        </AjaxSettings>
    </telerik:RadAjaxManager>

<telerik:RadAjaxLoadingPanel ID="radMembersLoadingPanel" runat="server" Height="75px"
        Width="75px" Transparency="2">
        <asp:Image ID="loadingImg" runat="server" ImageUrl="~/App_Themes/Default/images/loading.gif"
            AlternateText="Loading..." />
    </telerik:RadAjaxLoadingPanel>

<!-- RadComboBox   -->
<telerik:RadComboBox ID="radComboDatabase" runat="server" AutoPostBack="true" OnSelectedIndexChanged="radComboDatabase_SelectedIndexChanged"
                        AppendDataBoundItems="true">
                        <CollapseAnimation Type="OutQuint"></CollapseAnimation>
                        <Items>
                            <telerik:RadComboBoxItem Text="Select database" Value="-1" />
                        </Items>
                    </telerik:RadComboBox>