Can't add list: List Type field is required

I can't create lists with this module. after submission the error:

Fatal error: Call to undefined function debug() in /home/www/web46/web/drupal-5.1/includes/form.inc on line 562

with no page is returned. On refresh, the error 'List Type field is required.' is returned, but there is no List type field in the form.

Going to use simplenews instead