Index: taxonomy.php
===================================================================
--- taxonomy.php	(revision 19633)
+++ taxonomy.php	(working copy)
@@ -2647,7 +2647,7 @@
 
 	foreach ( $object_terms as $id => $value ) {
 		foreach ( $value as $taxonomy => $terms ) {
-			wp_cache_set($id, $terms, "{$taxonomy}_relationships");
+			wp_cache_add($id, $terms, "{$taxonomy}_relationships");
 		}
 	}
 }