=== modified file 'modules/system/system.module'
--- modules/system/system.module	2008-02-20 13:46:36 +0000
+++ modules/system/system.module	2008-02-25 23:34:38 +0000
@@ -1247,6 +1247,11 @@ function system_cron() {
     }
     db_query('DELETE FROM {files} WHERE fid = %d', $file->fid);
   }
+  $core = array('cache', 'cache_block', 'cache_filter', 'cache_page');
+  $cache_tables = array_merge(module_invoke_all('flush_caches'), $core);
+  foreach ($cache_tables as $table) {
+    cache_clear_all(NULL, $table);
+  }
 }
 
 /**