When I get blank pages it is usually caused by permissions problems. If you are using apache then the user you configured in the httpd.conf file (usually apache) must have permission to read the vBulletin files. There may be a better explaination of this on the board somewhere, if someone knows, please post a link.
If this is the cause; then it is just a webserver configuration problem and not a problem with LDAP or this mod.
Good luck ginab143