Warning: imagecopyresampled(): supplied argument is not a valid Image resource

php code:

$blank = imagecreatefromjpeg('blank.jpg');
.....
$pos_x = 0;
$pos_y = 0;
$pos_step = 10;
while ($get_images_i <= $get_images_n) {
      $ach_ico = imagecreatefromjpeg($get_images_links[1][$get_images_i]);
      imagecopyresampled($blank,$ach_ico,$pos_x,$pos_y,0,0,10,10,64,64);
      $pos_x = $pos_x + $pos_step;
      ImageDestroy($ach_ico);
      $get_images_i++;

}
.....
header("Content-type: image/png");
imagepng($blank);

Problem:
Warning: imagecopyresampled(): supplied argument is not a valid Image
resource

Details:
Apache 2.0.55 (Win32) php 5.2.9.
The array ($get_images_links) contains more than 50 url's.