The Dreaded Headers Already Sent error

<?php

    // RepeatSelectionCounter_2 Begin Loop

    $RepeatSelectionCounter_2_IterationsRemaining = $RepeatSelectionCounter_2_Iterations;

    while($RepeatSelectionCounter_2_IterationsRemaining--){

        if($RepeatSelectionCounterBasedLooping_2 || $row_Recordsetmultiprint){            

        $maxRows_Recordsetdisplayproducts = 10;

$pageNum_Recordsetdisplayproducts = 0;

if (isset($_GET['pageNum_Recordsetdisplayproducts'])) {

  $pageNum_Recordsetdisplayproducts = $_GET['pageNum_Recordsetdisplayproducts'];

}

$startRow_Recordsetdisplayproducts = $pageNum_Recordsetdisplayproducts * $maxRows_Recordsetdisplayproducts;

$colname_Recordsetdisplayproducts = "-1";

if (isset($_GET['invoiceid'])) {

  $colname_Recordsetdisplayproducts = $_GET['invoiceid'];

}

$paramInvoiceID_Recordsetdisplayproducts = "-1";

if (isset($row_Recordsetmultiprint['invoiceid'])) {

  $paramInvoiceID_Recordsetdisplayproducts = (get_magic_quotes_gpc()) ? $row_Recordsetmultiprint['invoiceid'] : addslashes($row_Recordsetmultiprint['invoiceid']);

}

mysql_select_db($database_midas0001, $midas0001);

$query_Recordsetdisplayproducts = sprintf("SELECT * FROM products  left join invoice on invoice.invoiceid = products.invoiceid WHERE products.invoiceid = %s AND invoice.print = '1' ORDER BY productid", GetSQLValueString($paramInvoiceID_Recordsetdisplayproducts, "int"));

$Recordsetdisplayproducts = mysql_query($query_Recordsetdisplayproducts, $midas0001) or die(mysql_error());

$row_Recordsetdisplayproducts = mysql_fetch_assoc($Recordsetdisplayproducts);

$totalRows_Recordsetdisplayproducts = mysql_num_rows($Recordsetdisplayproducts);?>

<?php require_once("../webassist/email/mail_php.php"); ?>

<?php require_once("../webassist/email/mailformatting_php.php"); ?>

<?php

if (!isset($_SESSION))session_start();

if ((($_SERVER["REQUEST_METHOD"] == "POST") && (isset($_SERVER["HTTP_REFERER"]) && strpos(urldecode($_SERVER["HTTP_REFERER"]), urldecode($_SERVER["SERVER_NAME"].$_SERVER["PHP_SELF"])) > 0) && isset($_POST)))     {

  //WA Universal Email object="mail"

  set_time_limit(0);

  $EmailRef = "waue_invoice-email_multi_comm_logo_2";

  $BurstSize = 200;

  $BurstTime = 1;

  $WaitTime = 1;

  $GoToPage = "confirminvoiceprintoption.php";

  $RecipArray = array();

  $StartBurst = time();

  $LoopCount = 0;

  $TotalEmails = 0;

  $RecipIndex = 0;

  // build up recipients array

  $CurIndex = sizeof($RecipArray);

  $RecipArray[$CurIndex] = array();

  $RecipArray[$CurIndex ][] = "".$row_Recordsetmultiprint['cust_email']  ."";

  $TotalEmails += sizeof($RecipArray[$CurIndex]);

  $RealWait = ($WaitTime<0.25)?0.25:($WaitTime+0.1);

  $TimeTracker = Array();

  $TotalBursts = floor($TotalEmails/$BurstSize);

  $AfterBursts = $TotalEmails % $BurstSize;

  $TimeRemaining = ($TotalBursts * $BurstTime) + ($AfterBursts*$RealWait);

  if ($TimeRemaining < ($TotalEmails*$RealWait) )  {

    $TimeRemaining = $TotalEmails*$RealWait;

  }

  $_SESSION[$EmailRef."_Total"] = $TotalEmails;

  $_SESSION[$EmailRef."_Index"] = 0;

  $_SESSION[$EmailRef."_Remaining"] = $TimeRemaining;

  while ($RecipIndex < sizeof($RecipArray))  {

    $EnteredValue = is_string($RecipArray[$RecipIndex][0]);

    $CurIndex = 0;

    while (($EnteredValue && $CurIndex < sizeof($RecipArray[$RecipIndex])) || (!$EnteredValue && $RecipArray[$RecipIndex][0])) {

      $starttime = microtime_float();

      if ($EnteredValue)  {

        $RecipientEmail = $RecipArray[$RecipIndex][$CurIndex];

      }  else  {

        $RecipientEmail = $RecipArray[$RecipIndex][0][$RecipArray[$RecipIndex][2]];

      }

      $EmailsRemaining = ($TotalEmails- $LoopCount);

      $BurstsRemaining = ceil(($EmailsRemaining-$AfterBursts)/$BurstSize);

      $IntoBurst = ($EmailsRemaining-$AfterBursts) % $BurstSize;

      if ($AfterBursts<$EmailsRemaining) $IntoBurst = 0;

      $TimeRemaining = ($BurstsRemaining * $BurstTime * 60) + ((($AfterBursts<$EmailsRemaining)?$AfterBursts:$EmailsRemaining)*$RealWait) - (($AfterBursts>$EmailsRemaining)?0:($IntoBurst*$RealWait));

      if ($TimeRemaining < ($EmailsRemaining*$RealWait) )  {

        $TimeRemaining = $EmailsRemaining*$RealWait;

      }

      $CurIndex ++;

      $LoopCount ++;

      session_commit();

      session_start();

      $_SESSION[$EmailRef."_Index"] = $LoopCount;

      $_SESSION[$EmailRef."_Remaining"] = round($TimeRemaining);

      session_commit();

      wa_sleep($WaitTime);

      include("../webassist/email/waue_invoice-email_multi_comm_logo_2.php");

      $endtime = microtime_float();

      $TimeTracker[] =$endtime - $starttime;

      $RealWait = array_sum($TimeTracker)/sizeof($TimeTracker);

      if ($LoopCount % $BurstSize == 0 && $CurIndex < sizeof($RecipArray[$RecipIndex]))  {

        $TimePassed = (time() - $StartBurst);

        if ($TimePassed < ($BurstTime*60))  {

          $WaitBurst = ($BurstTime*60) -$TimePassed;

          wa_sleep($WaitBurst);

        }

        else  {

          $TimeRemaining = ($TotalEmails- $LoopCount)*$RealWait;

        }

        $StartBurst = time();

      }

      if (!$EnteredValue)  {

        $RecipArray[$RecipIndex][0] =  mysql_fetch_assoc($RecipArray[$RecipIndex][1]);

      }

    }

    $RecipIndex ++;

  }

  $_SESSION[$EmailRef."_Total"] = 0;

  $_SESSION[$EmailRef."_Index"] = 0;

  $_SESSION[$EmailRef."_Remaining"] = 0;

  session_commit();

  session_start();

  if ($GoToPage!="")     {

    header("Location: ".$GoToPage);

  }

}

?>