we did find this in error_log
[04-Feb-2013 10:19:36] PHP Fatal error: Undefined class constant ‘VAR_DIRECTORY’ in /home/XXXXX/public_html/get.php on line 63
and this is line 63 from get.php: $varDirectory = $bp . $ds . Mage_Core_Model_Config_Options::VAR_DIRECTORY;
the error_log was 5GB big and only this error was writing all the time
Any Idea what there is wrong?