Fejl ved Header

Følgende kode videresender ikke på noget tidspunkt når jeg bruger header.
Jeg har prøvet at oprette en side med <? header("Location: fil.php"); ?> og det virker fint...

<?
session_start();
include("dbconnect.php");
error_reporting(E_ALL);
$allowedsize = $bannersize*1024;
if ($_FILES['imagefile']['type'] == "image/jpeg" || $_FILES['imagefile']['type'] == "image/pjpeg" || $_FILES['imagefile']['type'] == "image/gif"){
    if ($_FILES['imagefile']['size'] <= $allowedsize) {
        if ($debug) { echo "saving banner information to database<br>"; }
        mysql_query("INSERT INTO sources (path) VALUES ('$banner_url')") or die(mysql_error());
        $source = mysql_insert_id();
        mysql_query("INSERT INTO banners (user, str, source, dest, aktiv) VALUES ($login_user, '$banner_str', $source, '$banner_dest', 1)") or die(mysql_error());
        $banner = mysql_insert_id();
        mysql_query("INSERT INTO bannerstat (banner) VALUES ($banner)") or die(mysql_error());
        if ($debug) { echo "Success!<br>"; }
        $data = mysql_query("SELECT id FROM `banners` ORDER BY `id` DESC LIMIT 1");
        while ($row = mysql_fetch_array($data)) {
            $name = $row[id];
            if ($_FILES['imagefile']['type'] == "image/jpeg" || $_FILES['imagefile']['type'] == "image/pjpeg") {
                $name = $name.".jpg";
            } elseif ($_FILES['imagefile']['type'] == "image/gif") {
                $name = $name.".gif";
            }
        }
        if ($debug) { echo "Copying from temp folder<br>"; }
        copy ($_FILES['imagefile']['tmp_name'], "$bannerdir$name");
        if ($debug) { echo "Success!<br>"; }
        $banner_url = $bannerdir2.$name;
        mysql_query("UPDATE sources set path = '$banner_url' where id = $source");
        header("Location: user.php");
    } else {
        if ($debug) { echo "redirecting because of banner being too big (< $allowedsize bytes)"; }
        header("Location:  besked.php?besked=5");
        exit;
    }
} else {
    header("Location: besked.php?besked=4");
    exit;
}
?>