Please see this Jira issue which contains a new class_core.php file to use that will allow you to shut off display errors via your config.php file -
http://tracker.vbulletin.com/browse/VBIV-15862 (Note, you must first login to the vbulletin.com forums as a Licensed User before you may see the Jira issue.) After uploading the new file and adding the line to the config.php file, are you still having the same issue?