PHP warnings when new user is registered

Thanks for the quick fix on my previous request.

When a new user logs in, these PHP warnings appear:

* warning: array_fill(): Number of elements must be positive in /home/web/html/site/includes/database.inc on line 235.
* warning: implode(): Bad arguments. in /home/web/html/site/includes/database.inc on line 235.
* warning: array_keys(): The first argument should be an array in /home/web/html/site/modules/user/user.module on line 500.
* 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 p.perm FROM role r INNER JOIN permission p ON p.rid = r.rid WHERE r.rid IN () in /home/web/html/site/modules/user/user.module on line 500.

This is a new Drupal 6.2 site. I'm using pubcookie-6.x-1.1.tar.gz. The Profiles module is enabled. Error reporting is set to "E_ALL & ~E_NOTICE". I have LDAP enabled in pubcookie.

The new user account is created correctly. Tables user and authmap appear to be correct. After the initial burst of PHP warnings, the new user can login/logout without problems.

The log entry immediately before the warnings is "Session ID is ..." and immediately after is "User callback received for user N", then LDAP kicks in and pubcookie finishes up without complaining. Based on the sequence of log entries, I think the problem occurs when pubcookie.module executes

user_external_login_register($pubcookie_user, 'pubcookie');

The same warnings have been associated with Drupal 5 external authentication issues discussed at

http://drupal.org/node/109576
http://drupal.org/node/165642

I haven't spent much time with Drupal 6 so I don't really know where to start looking.