It sounds like the clue is in the page source. You need to see what the link says in there.
You may also want to look at your error_logs and see if there is anything in there. If you don't know where they are, ask your host.
This may or may not help - here is a page from the manual about troubleshooting blank or 'white' pages:
http://www.vbulletin.com/docs/html/blank_pages