If you’re running WordPress 2.1 trunk from SVN (currently at 2.1-alpha3, r4663) with Ultimate Tag Warrior (UTW) 3.141592 (the latest version as of today), UTW will lose all tags on a post when a new comment is made.
To fix this, edit the
ultimate-tag-warrior-actions*.php files (in your UTW directory, there should be one
-actions.php and one
-actions-wordpress2.php, simply edit both). In the function
ultimate_save_tags($postID), add the following lines right after the opening curly bracket:
if (!is_admin()) return $postID; if (!isset($_POST['tagset'])) return $postID;
Save the files and you should be all set.
The problem occurs because WordPress trunk calls the edit_post hook when new comments are added. UTW doesn’t check the environment and just assumes the admin wanted to delete all tags, and then dutifully removes the tags from the post.
The fix just does nothing when the edit_post hook gets called from outside the admin publish area.
Update: See also Thomas’ comment for the latest UTW version.