Many warnings when attempting to connect to Drupal 6.17

Hi,
I just enabled the WebDAV module in a fresh drupal-6.17 installation. When I access the webdav URL with a browser, the page shows many warnings. The webdav is working, though.

warning: array_fill(): Number of elements must be positive in /data/drupal/includes/database.inc on line 253.
warning: implode(): Invalid arguments passed in /data/drupal/includes/database.inc on line 253.
warning: array_keys() expects parameter 1 to be array, null given in /data/drupal/modules/user/user.module on line 513.
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 /data/drupal/modules/user/user.module on line 513.
warning: Invalid argument supplied for foreach() in /data/drupal/sites/all/modules/webdav/server.inc on line 198.
warning: Invalid argument supplied for foreach() in /data/drupal/sites/all/modules/webdav/webdav_listing.tpl.php on line 58.
warning: array_keys() expects parameter 1 to be array, null given in /data/drupal/modules/block/block.module on line 432.
warning: array_fill(): Number of elements must be positive in /data/drupal/includes/database.inc on line 253.
warning: implode(): Invalid arguments passed in /data/drupal/includes/database.inc on line 253.
warning: array_merge(): Argument #2 is not an array in /data/drupal/modules/block/block.module on line 433.
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 ') OR r.rid IS NULL) ORDER BY b.region, b.weight, b.module' at line 1 query: SELECT DISTINCT b.* FROM blocks b LEFT JOIN blocks_roles r ON b.module = r.module AND b.delta = r.delta WHERE b.theme = '' AND b.status = 1 AND (r.rid IN () OR r.rid IS NULL) ORDER BY b.region, b.weight, b.module in /data/drupal/modules/block/block.module on line 433.
warning: array_keys() expects parameter 1 to be array, null given in /data/drupal/sites/all/modules/views/views.module on line 480.