There are two lines in xmlrpc.php at the root of your wordpress blog that have:
$to_ping = $content_struct[‘mt_tb_ping_urls’]
Replace both of them with:
$to_ping_input = $content_struct['mt_tb_ping_urls'];
$to_ping = “” ;
if (is_array($to_ping_input)) {
foreach ($to_ping_input as $ping_url) {
$to_ping = $to_ping . $ping_url . “ ”;
}
}