I'm saying:
1) Check your error_logs (if you don't know where they are, ask your host). There may be something in there to tell you why the page is not working.
2) Try going through the installation instructions again and make sure it is properly installed.
3) If neither of those help you out, then here is a page from the manual about troubleshooting blank or 'white' pages:
http://www.vbulletin.com/docs/html/blank_pages