I'm trying to implement a GridView with paging inside a UpdatePanel. Everything works great when I do my first click. The paging kicks in and the next set of data is loaded quickly. However, when I then try to click a link for another page of data, I get the following error:

Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code returned from the server was: 12030

aspx code

    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <contenttemplate>
        <asp:GridView ID="GridView1" runat="server" CellPadding="2" 
                AllowPaging="true" AllowSorting="true" PageSize="20"
                OnPageIndexChanging="GridView1_PageIndexChanging"
                OnSorting="GridView1_PageSorting"
                AutoGenerateColumns="False">
            <Columns>
                <asp:BoundField DataField="ActivityLogID" HeaderText="Activity Log ID" SortExpression="ActivityLogID" />
                <asp:BoundField DataField="ActivityDate" HeaderText="Activity Date" SortExpression="ActivityDate" />
                <asp:BoundField DataField="ntUserID" HeaderText="NTUserID" SortExpression="ntUserID" />
                <asp:BoundField DataField="ActivityStatus" HeaderText="Activity Status" SortExpression="ActivityStatus" />
            </Columns>
        </asp:GridView>
    </contenttemplate>
</asp:UpdatePanel>

code behind

    private void bindGridView(string sortExp, string sortDir)
    {
        SqlCommand mySqlCommand = new SqlCommand(sSQL, mySQLconnection);
        SqlDataAdapter mySqlAdapter = new SqlDataAdapter(mySqlCommand);
        mySqlAdapter.Fill(dtDataTable);

        DataView myDataView = new DataView();
        myDataView = dt.DefaultView;

        if (sortExp != string.Empty)
        {
            myDataView.Sort = string.Format("{0} {1}", sortExp, sortDir);
        }

        GridView1.DataSource = myDataView;
        GridView1.DataBind();

        if (mySQLconnection.State == ConnectionState.Open)
        {
            mySQLconnection.Close();
        }

    }
        protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        GridView1.PageIndex = e.NewPageIndex;
        bindGridView();
    }
    protected void GridView1_PageSorting(object sender, GridViewSortEventArgs e)
    {

        bindGridView(e.SortExpression, sortOrder);

    }

any clues on what is causing the error on the second click?