With the following code, my browser is returning 'image not created or saved'. I assure you the location of the image exists.  So the line within the if statement is returning false for some reason, and yes GD is installed.  Any ideas?
if ($img = @imagecreatefromjpeg("/var/www/images/upload/1/1.jpg")) {
            $image_width = imagesx($img);
            $image_height = imagesy($img);
            $target_width = 150;
            $target_height = 150;
            if ($image_width > $image_height) {
                $percentage = ($target_width / $image_width);
            } else {
                $percentage = ($target_height / $image_height);
            }
            $new_image_width = round($image_width * $percentage);
            $new_image_height = round($image_height * $percentage);
            $imgResized = imagecreatetruecolor($new_image_width, $new_image_height);
            imagecopyresampled($imgResized, $img, 0, 0, 0, 0, $new_image_width, $new_image_height, $image_width, $image_height);
            imagejpeg($imgResized, $this->path, 100);
            imagedestroy($img);
            imagedestroy($imgResized);
            $this->storeThumbnailLocation();
        } else {
            die ("image was not created or saved");
        }