Index: module.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/module.inc,v
retrieving revision 1.93
diff -u -r1.93 module.inc
--- module.inc	7 Dec 2006 17:03:34 -0000	1.93
+++ module.inc	12 Jan 2007 14:13:40 -0000
@@ -320,7 +320,11 @@
  *   implemented in that module.
  */
 function module_hook($module, $hook) {
-  return function_exists($module .'_'. $hook);
+  static $hooklist = array();
+  if (!isset($hooklist[$module][$hook])) {
+    $hooklist[$module][$hook] = function_exists($module .'_'. $hook);
+  } 
+  return $hooklist[$module][$hook];
 }
 
 /**