You mean a completely blank white page? That means there was some kind of error when generating the page. Somewhere there's a page that deals with debugging blank pages but I don't remember where it is offhand. You could try creating a new style with no parent and see if that makes a difference. Also try temporarily disabling all plugins by putting
define('DISABLE_HOOKS', true);
in your config.php.
Edit: Here's the thing about blank pages:
https://www.vbulletin.com/docs/html/blank_pages