make change in php.ini file – cannot find this file for now 🙁

$type = getimagesize($file);

by otto – http://ottodestruct.com/,  thanks to post in http://lorelle.wordpress.com/2007/03/28/wordpress-thumbnail-size-limit-hack/

function raise_image_size_limit() {
return 8*1024*1024; // or whatever you want
}
add_filter('wp_thumbnail_creation_size_limit','raise_image_size_limit');

function custom_thumbnail_size() {
return 128; // or whatever you want
}
add_filter('wp_thumbnail_max_side_length','custom_thumbnail_size');