failed to open stream: Permission denied [CORE/cake/libs/file.php, line 146]

Warning (2): fopen(cakephp/app/tmp/cache/persistent/cake_core_dir_map) [function.fopen]: failed to open stream: Permission denied [CORE/cake/libs/file.php, line 146]

The main problem could be the access permission of the cache folder or the files within.

first try to set 777 permission to the app/tmp folder.

try clearing the cache.

If any of the persistent cache files have a different user say webadmin instead of apache, then that could result in these kind of issues