I've just created a sub-sub-category (ie its parent has a parent) with the name 'General' and slug 'general' and it was created correctly showing at the top of the list as Event - Type - General.
I then reloaded the page ie /wp-admin/categories.php and it didn't appear in the list with all the other sub-sub-categories at all! I thought I was going mad wondering if I had actually created it and tried to create it again but was told that the name already existed!
Then I wondered if it would appear in the list when I create a post and there it was in the list of categories in its correct sub-sub-category position as I would expect. I looked with phpMyAdmin at the database and of course it was there at the end of the wp_terms table.
I created all the categories before the one today in an earlier version of WordPress - probably 2.5 - now on the latest 2.7.1.
So I am wondering if there is a strange bug in /wp-admin/categories.php stopping the display of this new category? I've disabled plugins that I think might be interfering with this display like Admin Management Xtended and Reveal IDs for WP Admin but no change.
I have a test version of my site on a free host which has almost the same configuration, but not completely, and I found the same problem when I tried to create this new category. So I've deactivated all the plugins on this test site and still don't have the new category appearing on /wp-admin/categories.php.
Can anyone else reproduce this strange anomaly?