That indicates that Drupal needed more memory than PHP was allowed to give it.
Increase PHP's memory limit, either by adding:
memory_limit = 12Mto your php.ini file (recommended, if you have access)
ini_set('memory_limit', '12M');in your sites/default/settings.php file
php_value memory_limit 12Min your .htaccess file in the Drupal root
Some hosts allow a PHP.ini in the root of your site.
Depending on the amount of modules you have enabled and their 'impact' on the site you may need to increase the memory_limit even more (so