ASP.net drop down list not working in google chrome

Question

I created Aps.net Application in which I am loading reports from database... I am facing a problem with drop down list ... this is working fine in internet explorer but not working in google chrome... here is the image of IE :

here is the image of Chrome...

the arrow is marking the line which is showing on clicking drop down button... Kindly help me out... here is the HTML code

<telerik:RadComboBox ID="ddlMonths" Width="125" Skin="Vista" runat="server" EmptyMessage="Select Month">
                                                                                        <Items>
                                                                                            <telerik:RadComboBoxItem runat="server" Text="January" Value="1" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="February" Value="2" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="March" Value="3" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="April" Value="4" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="May" Value="5" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="June" Value="6" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="July" Value="7" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="August" Value="8" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="September" Value="9" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="October" Value="10" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="November" Value="11" />
                                                                                            <telerik:RadComboBoxItem runat="server" Text="December" Value="12" />
                                                                                        </Items>
                                                                                        <CollapseAnimation Type="OutQuint" Duration="200"></CollapseAnimation>
                                                                                    </telerik:RadComboBox>

Here is the usage of drop down dialog code:

ddlMonths.SelectedValue = DateTime.Now.Month.ToString();

Answer 1

Set EnableOverlay to true for the combo box. My best guess with the available info is that the content below the dropdown is some heavyweight content like a flash or pdf plugin that hides HTML.