When Someone ads a friend now we get the following message.. Any idea why?

Anyone?

Many thanks...

Warning: Invalid argument supplied for foreach() in /home/mycrossd/public_html/includes/libs/common.inc.php on line 241

Warning: implode() [function.implode]: Invalid arguments passed in /home/mycrossd/public_html/includes/libs/common.inc.php on line 244

Warning: Cannot modify header information - headers already sent by (output started at /home/mycrossd/public_html/includes/libs/common.inc.php:241) in /home/mycrossd/public_html/includes/libs/common.inc.php on line 326