problem in downloading the excel file through IIS8

Question

when i run program locally it gives correct answer.. when i run on IIS it gives error...

error when download the excel page.... the error is 

The remote procedure call failed. (Exception from HRESULT: 0x800706BE)

the code is

protected void Expgo_Click(object sender, EventArgs e)

    {

        /*************************************

         * On export click, select date range 

         * Generate weekley TimeSheet Report

         ************************************/

        QueryRet Value = new QueryRet();

        String StartCalDate;

        String EndCalDate;

        StartCalDate = ExpCalStart.SelectedDate.ToString();

        EndCalDate = ExpCalEnd.SelectedDate.ToString();

        if (StartCalDate == EndCalDate)

        {

            Weekview.SetActiveView(Blank);

            lblerr.Text = "Please Select Range of Dates.";

            lblerr.Visible = true;

        }

        else

        {

            ExcelApp = new Excel.Application();

            ExcelApp.Visible = false;

            ExcelWork = (Excel._Workbook)(ExcelApp.Workbooks.Add(Missing.Value));

            string strCurrentDir = Server.MapPath("~/TimeSheets/");

            RemoveFiles(strCurrentDir);//removes all .xls files in directory

            DateTime Daylist;

            String Query;

            /*******************************************

             * Select all WeekStartDates in the given range of dates

            *********************************************/

            Query = "SELECT DISTINCT WeekStartDate FROM TimeSheetBreakDown";

            Query += " Where Date >= '" + Convert.ToDateTime(StartCalDate).ToString("yyyy/MM/dd") + "' AND Date<='" + Convert.ToDateTime(EndCalDate).ToString("yyyy/MM/dd") + "'";

            ArrayList DistinctStart = Value.ExecuteQry(Query);

            if (ExcelWork.Worksheets.Count <= DistinctStart.Count)

            {

                ExcelWork.Worksheets.Add(Missing.Value, Missing.Value, DistinctStart.Count - ExcelWork.Worksheets.Count + 1, Missing.Value);

            }

            for (int s = 0; s < DistinctStart.Count; s++)

            {

                /****************************************

                 * For each of the week which come under date selected

                 * Generate One Excel Work Sheet

                 ****************************************/

                try

                {

                    Query = "SELECT distinct Date FROM TimeSheetBreakDown WHERE (WeekStartDate = '" + DistinctStart[s] + "' AND Day='1') order by date";

                    Daylist = DateTime.Parse(Value.SelectQry(Query));

                    /******************************************

                     * From the Distinct StartDate Get (Date of) Monday of that week

                     * From Monday Calculate other Days From TimeSpan

                     * ****************************************/

                    mon = Daylist;

                    tue = Daylist + new TimeSpan(1, 0, 0, 0);

                    wed = Daylist + new TimeSpan(2, 0, 0, 0);

                    thu = Daylist + new TimeSpan(3, 0, 0, 0);

                    fri = Daylist + new TimeSpan(4, 0, 0, 0);

                    sat = Daylist + new TimeSpan(5, 0, 0, 0);

                    sun = Daylist + new TimeSpan(6, 0, 0, 0);

                }

                catch (Exception X)

                {

                    lblerr.Text = X.Message + " Looks like you are Exporting Blank TimeSheet";

                    lblerr.Visible = true;

                }

                finally

                {

                    GC.Collect();

                    /***************************************

                     * Generates one Excel WorkSheet (Gives TimeSheet of that Week)

                    ****************************************/

                    GenerateExcel(s + 1);

                }

            }

            DistinctStartCount = DistinctStart.Count + 1;

            SummarySheet();

            ExcelApp.Visible = false;

            ExcelApp.UserControl = false;

            String FileName = "" + User.Identity.Name + ".xlsx";

            ExcelWork.SaveCopyAs(strCurrentDir + FileName);/* shows error at this line */

            String TimeSheetPath = (String)System.Configuration.ConfigurationManager.AppSettings["TimeSheetPath"].ToString();

            string strMachineName = Request.ServerVariables["SERVER_NAME"];

            Expgo.Text = "<A href=http://" + strMachineName + TimeSheetPath + FileName + ">Download TimeSheet</a>";

/* when i click download TimeSheet link */

            //TODO: CLean Up...

            ExcelApp.Quit();

            System.Runtime.InteropServices.Marshal.ReleaseComObject(ExcelRange);

            System.Runtime.InteropServices.Marshal.ReleaseComObject(ExcelApp);

            System.Runtime.InteropServices.Marshal.ReleaseComObject(ExcelSheet);

            System.Runtime.InteropServices.Marshal.ReleaseComObject(ExcelWork);

            ExcelSheet = null;

            ExcelWork = null;

            ExcelApp = null;

            GC.Collect();

        }

    }