Can not import members in E-newsletter

When I try to import members in a group, I get the messages that the page can not be found.
After upgrade to 3.5 word-press the next line is on the top of the e-newsletter plugin:

"Warning: Missing argument 2 for wpdb::prepare(), called in /www/e/l/l/ellad2.com/public_html/wp-content/plugins/e-newsletter/email-newsletter-files/class.functions.php on line 588 and defined in /www/e/l/l/ellad2.com/public_html/wp-includes/wp-db.php on line 990"