i dunno if theres some other way
but heres a way that can work
make a new folder and a database in your server
install a fresh copy of vbulletin [same version as you are using now]
DO NOT DELETE OLD FILES AND DATABASE
then drop these tables from your old database: tagcontent, tag, searchcore, searchgroup and searchlog
then export these same tables from your new database to your old one
TAKE DATABASE BACKUP BEFORE TRYING THIS