First time auth problem

I use drupal 5.1. All works fine - thanks for great module! - except one little bug.
Then user authorizes for the first time he get this message:

warning: array_keys() [function.array-keys]: The first argument should be an array in /home/slovao/public_html/drakon/modules/user/user.module on line 361.
warning: implode() [function.implode]: Bad arguments. in /home/slovao/public_html/drakon/modules/user/user.module on line 361.
user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1 query: SELECT DISTINCT(p.perm) FROM role r INNER JOIN permission p ON p.rid = r.rid WHERE r.rid IN () in /home/slovao/public_html/drakon/includes/database.mysql.inc on line 172.

Nevertheless authorization is successful, and next time this message doesn't appear. But it's strange to see. How to get rid of it?