this is a problem with using multiple select lists.
Multiple select lists pass the selections as an array, the array needs to be converted to a comma separated list.
add the following code at line 1 of your page to convert the array:
<?php
if($_SERVER["REQUEST_METHOD"] == "POST") {
foreach($_POST as $key => $val) {
if(is_array($_POST[$key])) $_POST[$key] = implode(", ", $_POST[$key]);
}
}
?>