AjaxControlToolkit - TabPanel with dropdown list - Unable to select

Question

I have a used the AjaxControlToolkit with TabPanel and UpdatePanel. The UpdatePanel contains a radio button list and based on the selection the content below the radio buttons will be changed.

<asp:Panel runat="server" ID="Pnl">
    <ajaxToolkit:TabContainer runat="server" ID="Container" CssClass="tabCont" ActiveTabIndex="0">
        <ajaxToolkit:TabPanel runat="server" ID="tab">
            <asp:UpdatePanel runat="server" ID="UpdatePanel"  UpdateMode="Conditional">
                <asp:RadioButtonList runat="server" ID="ActionType" RepeatDirection="Horizontal" AutoPostBack="true" OnSelectedIndexChanged="OnUserActions" />
                <asp:DropDownList runat="server" ID="FormatList"  CssClass="ddlCss" />
            ...
            </asp:UpdatePanel>
        </ajaxToolkit:TabPanel>
    </ajaxToolkit:TabContainer>
</asp:Panel>

When user tries to selects a value from the dropdown using mouse the dropdown collapses immediately before selection. The same does not happen if the dropdown is outside the Ajax TabPanel.

I tried to debug this and found the below method was getting called when the drop down collapses but could not find the caller or how to fix it.

// MicrosoftAjax.js
Function.createCallback = function (b, a)
{
    return function ()
    {
        var e = arguments.length;
        if (e > 0)
        {
            var d = [];
            for (var c = 0; c < e; c++) d[c] = arguments[c];
            d[e] = a;
            return b.apply(this, d)
        }
        return b.call(this, a)
    }
};

Is there a way to disable the callback during the mouse move?