When I try to send an email campaign the emails are not sent and I get a PHP error:
Undefined variable: join in /etc/httpd/htdocs/SugarCE-Full-6.1.3/include/utils.php.

When I sent test emails it worked perfectly it only fails when I try to send the real emails.

Sugar Version CE 6.1
Mysql Version: 5.0.77-log
PHP Version 5.2.10

What can I do to fix this?
Thanks