Latest version of wordpress, the plugin works on the primary site in multisite but on secondary sites, throws this error on submission of new email address:
Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in /SITEPATH/sml.php on line 273
http://wordpress.org/extend/plugins/mail-subscribe-list/
Note: If I disable this at the Network level, and enable the plugin only at the site level (for each site) then it works fine.