AutoComplete Extender - Scroll bar causes results to close?

Hi,

I have had a website running using a textbox, autocomplete extender, and autocompletedropdownpanel. Basically when a user starts typing a name into the text box the results appear in a few seconds. Since there can be hundreds of rows I need a scroll bar. Then the use just selects the name. For some reason, it is now broken (maybe update with IE? as it works fine in Chrome) Now when a user uses the scroll bar it automatically closes the results and is unable to make a selection. I have not been able to find a solution on the web for this. Is there an updated ajax kit I need to use? If so how do I go about replacing it? Or is there something to my code I can add or change? TIA

<asp:Panel ID="autocompleteDropDownPanel" runat="server"
            ScrollBars="Auto" Height="200px" Font-Size="Medium"
            HorizontalAlign="Left" Wrap="False" /><asp:AutoCompleteExtender ID="AutoCompleteExtender" runat="server"
        DelimiterCharacters="" Enabled="True" ServicePath="AutoComplete.asmx"
                ServiceMethod="GetCompletionList" TargetControlID="DoctorNameTextBox"
                UseContextKey="true" ContextKey="StateDropDown"
                CompletionListElementID="autocompleteDropDownPanel"
                onclientitemselected="getSelected"
                ShowOnlyCurrentWordInCompletionListItem="True" CompletionInterval="100"
                MinimumPrefixLength="2"></asp:AutoCompleteExtender>