MySQL Error : Duplicate column name 'ucash_perthread'

How Do I fix this?

Database error in vBulletin 3.5.2:

Invalid SQL:
ALTER TABLE forum
ADD `ucash_perthread` varchar(20) DEFAULT '1' NOT NULL ,
ADD `ucash_perreply` varchar(20) DEFAULT '1' NOT NULL ,
ADD `ucash_perview` varchar(20) DEFAULT '1' NOT NULL;

MySQL Error : Duplicate column name 'ucash_perthread'
Error Number : 1060
Date : Tuesday, January 17th 2006 @ 01:42:16 AM
Script : http://www.southernsportbike.com/tes...es&hacks=uCash
Referrer : http://www.southernsportbike.com/tes...es&hacks=uCash
IP Address : 24.240.28.24
Username : test
Classname : vb_database