Index: user_mailman_register.module
===================================================================
--- user_mailman_register.module	(revision 151)
+++ user_mailman_register.module	(working copy)
@@ -909,6 +909,11 @@
   }
   $filter = '![^abcdefghijklmnopqrstuvwxyz0-9-_ ]+!s';
   $list_clean = preg_replace($filter, '-', drupal_strtolower($list->name));
+
+  if (empty($account->status)) {
+    return FALSE;
+  }
+
   //Account is an array of roles to check
   if (is_array($account) && !empty($account)) {
     $list_roles = user_roles(FALSE, 'can subscribe to '. $list_clean);