Extend block_manager to handle sidebar blocks. get_available has become get_available_admin_blocks, get_list becomes get_admin_list. Create new functions get_available_site_blocks which will look for gallery_block get_available_site_blocks

modules/comment/helpers/comment_block.php

@@ -18,7 +18,7 @@
  * Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA  02110-1301, USA.
  */
 class comment_block_Core {
-  static function get_list() {
+  static function get_admin_list() {
     return array("recent_comments" => t("Recent Comments"));
   }