If you find an entry reading 'Could not determine temp directory, please specify a cache_dir manually' in the error log files of the Magento system because the navigation in the admin area stopped working shortly after a fresh Magento installation, this error can be fixed quickly
by replacing the line
'cache_dir' => 'null',
or
'cache_dir' => null,
in the file /lib/Zend/Cache/Backend/File.php with
'cache_dir' => 'tmp/',
and then creating the "tmp" directory in the Magento shop's installation directory and assigning it the necessary permissions. Occurred after installing Magento 1.7.0.2 on a subdomain.
