User warning when creating new Taxonomy terms. "Duplicate entry"

Sample error message:

user warning: Duplicate entry 'taxonomy/term/9-' for key 2 query: INSERT INTO url_alias (src, dst, language) VALUES ('taxonomy/term/', 'taxonomy/term/9', '') in /nfs/disk/data/www/httpd-docs/tools/drupal/6.11/modules/path/path.module on line 112.

Error generation process: After terms are created, if user clicks on the "list" tab to view the list, and then reorders the list to put child items under parent items, the error message occurs.

Occurred three times out of three attempts. Does not appear to affect functionality. Does not occur when no children are in list.