Underlig fejl med upload script

Hej, jeg får denne fejl på mit webhotel

Warning: imagejpeg() [function.imagejpeg]: Unable to access upload/small825686Unavngivet.JPG in /home/xxxxx.dk/web/www/farmerservice/uptest.php on line 56

Warning: imagejpeg() [function.imagejpeg]: Invalid filename 'upload/small825686Unavngivet.JPG' in /home/xxxxx.dk/web/www/farmerservice/uptest.php on line 56

men får den ikke på hotserv.dk's webhotel ?
havd kan det skyldes?

Her får i koden:
<?php
$konfiguration["upload_bibliotek"] = "./upload/";
$konfiguration["max_stoerrelse"] = "1000000000000000000000000000000000000000000000000000000000000000000000000000";

$fra = $_FILES["upfil"]["tmp_name"];
$fra2 = $_FILES["upfil"]["name"];
$til = $konfiguration["upload_bibliotek"] . $_FILES["upfil"]["name"];

$fil_stoerrelse = filesize($fra)/1024;
if($fil_stoerrelse > $konfiguration["max_stoerrelse"]) {
  die("Filen er for stor");
}

if(function_exists("move_uploaded_file")) {
  move_uploaded_file($fra, $til);
$newfilename = "".rand(1, 1000000)."".$fra2."";
$newfilename2 = "upload/". $newfilename ."";
rename($til, $newfilename2);
} else {
  copy($fra, $til);
  rename($til, $newfilename2);
}
$pic = "upload/". $newfilename ."";
$thumb = "upload/small". $newfilename ."";
Thumb($pic, $thumb);

    function Thumb($sourcefile, $targetfile) {
    $size = 230;
    switch ($_FILES['upfil']['type']) {
    case "image/gif":
    $source_id = imageCreateFromGIF($sourcefile);
    break;
    case "image/jpeg":
    $source_id = imageCreateFromJPEG($sourcefile);
    break;
    case "image/png":
    $source_id = imageCreateFromPNG($sourcefile);
    break;
    default:
    echo "Sorry, but the file you uploaded was not a GIF, JPG, or .PNG file.<br>";
    }
    #$source_id = $format;
    #$source_id = imageCreateFromJPEG($sourcefile);
    $source_x = imagesx($source_id);
    $source_y = imagesy($source_id);
    $delta = $size/max($source_x, $source_y);
    $dest_x = round($source_x*$delta);
    $dest_y = round($source_y*$delta);
    $target_id=imagecreatetruecolor($dest_x, $dest_y);
    imagecopyresampled($target_id,$source_id,0,0,0,0, $dest_x,$dest_y, $source_x,$source_y);
    switch ($_FILES['upfil']['type']) {
    case "image/gif":
    imagegif($target_id,$targetfile,100);
    break;
    case "image/jpeg":
    imagejpeg($target_id,$targetfile,100);
    break;
    case "image/png":
    imagepng($target_id,$targetfile,100);
    break;
    default:
    echo "Sorry, but the file you uploaded was not a GIF, JPG, or .PNG file.<br>";
    }
}
?>