--- includes/install.inc	Fri Nov 27 04:57:16 2009
+++ includes/install.inc	Tue Dec 01 12:20:44 2009
@@ -491,8 +491,12 @@
  */
 function drupal_get_install_files($module_list = array()) {
   $installs = array();
+  $installManifest = drupal_system_listing('/.install$/', 'modules');
+  //not every module in module_list has to have an .install file
   foreach ($module_list as $module) {
-    $installs = array_merge($installs, drupal_system_listing('/' . $module . '.install$/', 'modules'));
+    if(isset($installManifest[$module])){
+      $installs[$module] = $installManifest[$module];
+    }
   }
   return $installs;
 }