RadComboBox takes a long time to expand

Question

Q:

I use RadComboBox to filter my large list but i face two problems :

1- The dropdown expanding takes long time !!

2- the filtering just happens in firefox ,no filtering in internet explorer!!

my .aspx:

    <td dir="rtl">
         <asp:RequiredFieldValidator ID="RequiredFieldValidator18" runat="server" ControlToValidate="ddl_mainLect"
         Display="Dynamic" ErrorMessage="*" InitialValue="-1" ValidationGroup="L">*</asp:RequiredFieldValidator>
         <telerik:RadComboBox ID="ddl_mainLect" runat="server" Filter="StartsWith" MarkFirstMatch="true"
         Width="350px" Skin="Outlook" CausesValidation="False">
        </telerik:RadComboBox>
     </td>

Answer 1

As far as number one is concerned, this documentation may help you.

For your second issue, are you using the most recent version of the RadControls? If not you should try upgrading.