Index: wp-admin/edit-tags.php
===================================================================
--- wp-admin/edit-tags.php	(revision 13020)
+++ wp-admin/edit-tags.php	(working copy)
@@ -329,11 +329,10 @@
 </div>
 
 <?php 
-if ( 'category' == $taxonomy ) 
-	do_action('add_category_form_fields');
-else
-	do_action('add_tag_form_fields', $taxonomy);
-do_action('add_' . $taxonomy . '_form_fields', $taxonomy);
+if ( 'category' != $taxonomy )
+	do_action('add_tag_form_fields', $taxonomy); // back compat.
+if ( 'tag' != $taxonomy ) // prevent back compat hook from running again.
+	do_action('add_' . $taxonomy . '_form_fields', $taxonomy);
 ?>
 
 <p class="submit"><input type="submit" class="button" name="submit" id="submit" value="<?php esc_attr_e('Add Tag'); ?>" /></p>