TYPO3 Core

7.3.1 (as seen from the path in the error-message)
extensions are nearly none as I just started to experiment with defining new CEs
some settings from LocalConfiguration.php:

return array(
    'BE' => array(
        'debug' => '1',
        'explicitADmode' => 'explicitAllow',
        :
        ),
    :
    'SYS' => array(
        'caching' => array(
            'cacheConfigurations' => array(
                'extbase_object' => array(
                    'backend' => 'TYPO3\\CMS\\Core\\Cache\\Backend\\Typo3DatabaseBackend',
                    'frontend' => 'TYPO3\\CMS\\Core\\Cache\\Frontend\\VariableFrontend',
                    'groups' => array(
                        'system',
                    ),
                    'options' => array(
                        'defaultLifetime' => 0,
                    ),
                ),
            ),
        ),
        'clearCacheSystem' => '1',
        'devIPmask' => '*',
        'displayErrors' => '1',
        'enableDeprecationLog' => '',
        'encryptionKey' => '07...f1',
        'exceptionalErrors' => 28674,
        'isInitialInstallationInProgress' => FALSE,
        'sitename' => 'T3 7.3',
        'sqlDebug' => '1',
        'systemLogLevel' => '0',
        't3lib_cs_convMethod' => 'mbstring',
        't3lib_cs_utils' => 'mbstring',
    ),
);
?>    

reproducing:
just go to "user settings" and click the button at "Clear Temporary Data"